Antimicrobial activity of cotton fabric treated with extracts from the lotus plant

Abstract

This study evaluated the application of medicinal plants to fabric finishes and the functionality of the fabrics finished with ethanolic extracts of the lotus plant, such as lotus leaf, lotus pot and lotus seed. Treated cotton was dyed a light orange and yellow-green color using lotus pot and lotus leaf, respectively, and the color difference ( $Δ E$ ) of fabrics before/after treatment with extract solution of lotus leaf was a maximum of 36.4. When the processing concentration of extract solution and treatment temperature of cotton fabric were increased, the color and color ingredient uptake increased, but the optimal processing time was found to be 30 minutes. Regarding the dyeing properties, the fabrics treated with the lotus leaf extract showed the best color in terms of color intensity, whereas the antibacterial activity was highest in the case of fabric treated with lotus pot extract. Antibacterial activity was significant in the order of lotus pot > lotus leaf > lotus seed. The fabric treated with the lotus leaf extract exhibited significant antibacterial activity only when it was treated at high concentrations (>8%), whereas the fabric treated with the lotus pot extract showed significant antibacterial activity even when treated at low concentrations (4%) or low temperatures (40℃). Accordingly, ethanolic lotus pot extract is recommended as an environment-friendly antibacterial finishing.

Keywords

Lotus pot lotus leaf lotus seed antibacterial finish processing condition

Textiles with antimicrobial properties are gaining interest. Pathogenic microbes can transfer infectious diseases and cause odor, degradation and discoloration of garments. Indeed, textile fibers provide an excellent substrate for the growth of micro-organisms. Therefore, there is a great demand for textiles with antimicrobial or self-cleaning properties.^1–3

With the growing concern for the environment, the use of natural products to impart various functions to textiles has attracted increasing attention. The potential use of Citrus grandis Osbeck for its antimicrobial effect on fabrics has been examined.⁴ Aloe vera extract and its natural antibacterial finishing for textile applications has also been investigated.⁵ Several reports have confirmed that natural dyes can be used not only to provide color but also reduce microbial growth (Mahonia napalaulensis D.C., Rheum undulatum L.).^4–7 Like these, many natural resources that impart antimicrobial properties to textiles were found and investigated deeply

On the other hand, there are no reports of the use of lotus (Nelumbo nucifera) extracts as a textile finish. Moreover, the dyeing performance of the lotus has not yet been examined. Lotus is a well-known medicinal plant, and extracts of rhizomes, seeds, flowers and leaves have been reported to have therapeutic potential.^8,9

Moreover, research on the tuber and leaf extracts of Nympaea lotus (Nymphaeceae) suggests a scientific basis for its use against pathogenic microbes.^10,11 The ethanolic extracts of lotus leaves were reported to have good antimicrobial activity against bacteria.¹² Tuber extracts were revealed to contain bio-active compounds such as tannins, flavonoids and alkaloids, which are effective against bacterial and fungal infections.¹¹

In this context, this study attempted to create a novel, eco-friendly and functional fabric utilizing the medicinal effects of the lotus plant. Thus, the lotus plant’s antibacterial activity and color production on textiles was investigated.

Experiment

Specimen and reagent

Scouring and bleaching of specimens

The fabrics used in the experiment were 100% cotton plain white fabrics that had been scoured and bleached. The white cotton fabric used was a plain weave, with yarn number of 30 Ne_c × 30 Ne_c, fabric count of 146 × 134/5 cm², fabric weight of 102 ± 5 g/m², and fabric thickness of 0.29 ± 0.02 mm. Scouring was done for 2 hours with water (water to fabric ratio of 40: 1) and Na₂HCO₃ (10% of fabric weight) at 70–80℃. The fabric was rinsed with distilled water for 10 minutes, dehydrated and then dried. To bleach the white fabrics, they were boiled at 80–90℃ for one hour with 13 g/L of H₂O₂, 1 g/L of NaOH and 1 g/L of a nonionic surfactant (TritonX100, Sigma) in distilled water (water to fabric ratio of 40: 1). The resulting fabric was then cleaned for 10 minutes with 90℃ distilled water and twice with cold water for 10 minutes before drying.

Preparation of lotus plant

The lotus materials used in this experiment were acquired from farms in Andong, Gyeongnam province, of South Korea. The lotus leaves, pots and seeds were collected around July/August 2012 and then cleaned with tap water and rinsed with ethanol and dried. The relevant volume was ground with ethanol for use. Lotus pots and seeds were separated from each other, and the seeds were peeled prior to use.

Experimental method

Ethanol extraction method

Lotus leaves, pots and peeled seeds were separately ground into a 3–5 mm particle size and extracted with 99.9% ethanol. During this process, ethanol evaporation was prevented by blocking the bottle entrance using the bottle cap with a 1:10 proportion of the weight ratio lotus: ethanol and soaking the lotus in the ethanol bottle for 48 hours. A higher concentration of ethanol extraction was suggested to contain less soluble solids and exhibit higher antibacterial activity.¹³ Each extracting liquid was prepared using the low temperature decompression and extraction method at 40–60℃ using the rotary vacuum evaporator (R-200, Buchi, Switzerland), and after obtaining the powder from extracting liquid, fresh ethanol (100 cc) was added to dissolve the powder. The pH of leaf and pot extracts (originally pH 5) was adjusted to pH 6 by adding one or two drops of ammonia solution. From this extract solution we made 4%, 6%, 8%, 10% and 12% dyeing solutions by adding distilled water.

GC-MS Analysis of the lotus extracts

Each ethanol extract was analyzed using gas chromatography-mass spectrometer (Bruker 3800 GC, 1200 L single quadrupole, Germany), and the analysis conditions were as follows. Elemental segregation was conducted with the column description of Agilent DB-5MS: 30 m × 0.25 mm id × 0.25 µm filled with 5% phenyl–95 % dimethylpolysiloxane. The experiment was conducted at an initial GC oven temperature of 70℃ for 3 minutes, temperature was then increased to 300℃ at a rate of 2℃/min, and was maintained at that temperature for 5 minutes. The injector and detector temperatures were 250℃ and 220℃, respectively.

Treatment method

Two sheets of 10 cm × 10 cm-sized cotton fabric were weighed (average weight of the specimens per unit was 3.5 g). The treatment solution was prepared in a flask from dilution of 100% solution with distilled water (solution to specimen ratio 30: 1). The specimens were added into the beaker after warming up in a double boiler, and the temperature of dye solution was increased to the correct temperature. Ethanol in dye solution was evaporated while dyeing and the treated fabrics were washed and line-dried overnight. The specimens in each dyeing solution beaker were processed under the following conditions: five conditions of treatment concentrations, four conditions of treatment temperatures, and four conditions of treatment times.¹⁴ In the first condition, the treatment concentrations were varied: the cotton fabrics were dyed with concentrations of 4%, 6%, 8%, 10% and 12% of the weight of bath (owb) and at 80℃ for 60 minutes. 80℃ was selected because the high temperature might change the color ingredient of lotus extracts, and differences between the treatment effects were more pronounced under 80℃. In the second condition, the cotton fabrics were dyed at 40℃, 60℃, 80℃ and 100℃ at a 4% concentration (owb) for 60 minutes. And in the final condition examining the treatment effects according to processing time, the cotton fabrics were dyed at 80℃, at a 4% concentration (owb) for 30, 60, 90 and 120 minutes.

Surface color reading and color ingredient uptake

The surface color reading and coloring component uptake of the treated specimens were determined by measuring Hunter’s Lab value at a D65 light source and at an observation angle of 10° using a color reader (Color I5D, X-rite Corp. U.S.A) which is the value of tri-stimulus color to the human eye. We used the K/S value as color ingredient uptake by fabrics and calculated the uptake using the following Kubelka Munk equation, where the spectral reflectance, R, was measured at 400 nm, K is proportional to the dyeing concentration, and S is dependent on the characteristics of fabric surface.¹⁵

K / S = \frac{(1 - R) 2}{2 R}

(1)

K: Extinction coefficient

S: Scattering coefficient

R: Spectral reflection (0 < R = 1)

Test of antibacterial activity

The antimicrobial properties of each extract from lotus leaf, pot and seed was determined using two methods, an antibacterial activity test on the crude liquid and an antibacterial degree test on the treated fabrics. The test bacteria included Staphylococcus aureus (ATCC 6538) and Klebsiella pneumonia (ATCC 4352). Antibacterial activity of the crude liquid was measured using the zone of inhibition (Halo test, Agar diffusion plate test: ISO KS K 20645). In each sterilized dish of 25 mL nurture, three 8 mm wells were holed and a 150 µl of distilled water and two 150 µl of 100% solution were inserted after the ethanol from the extract solutions evaporated. The result is shown as the zone of inhibition (W/mm: width of clear zone inhibition in mm).

The antibacterial degree of the cotton fabrics treated with the lotus extracts was determined by measuring the reduction ratio of bacterial growth (antibacterial activity test: KS K 0693). The concentrations of the cultures were 1.1 × 10⁵ (colony forming unit (CFU)/Ml) for Staphylococcus aureus and 1.3 × 10⁵ (CFU/Ml) for Klebsiella pneumonia. To measure the antibacterial degree of the cotton fabrics dyed with the lotus extracts, bacteria was cultured in a test and control piece of cotton (0.4 g) according to the standard test method. The number of live bacteria after 18 hours was measured, and the reduction ratio of bacteria was measured and expressed. The reduction ratio of bacteria was tested by measuring the bacteriostatic ratio using the following equation:

Bacteriostatic ratio (%) = \frac{B - A}{B} = 100

(2)

A: Number of bacteria regenerated in the cultured test piece

B: Number of bacteria regenerated in the cultured control piece

A & B are the average value of three replications

Results and discussions

Component analysis of lotus extracts

Most of the extracts were composed of fatty acids, which can partly explain the antimicrobial activity (Figure 1). An aromatic compound, neophytadiene (C₂₀H₃₈) was detected in the lotus leaf (Retention Time: RT 51.091, matching: 91.7%, area—3.26%) and lotus pot (RT: 50.940, matching 89.8%, area—1.98%), but was not detected in the lotus seed. These antibacterial components have also been detected in leaf tobacco.¹⁶ In addition, ethyl linoleolate (C₂₀H₃₆O₂), a major component of flower perfume and essential oil, was detected in the lotus leaf, pot and seed extracts. The highest level of ethyl linoleolate was measured in lotus pots (RT: 66.663, matching: 89.6%, area—28.36%), followed in order by lotus leaves (RT: 66.657, matching: 94.0%, area—10.56%) and lotus seeds (RT: 66.339, matching: 90.9%, area—9.98%).

Figure 1.

GC-MS trace showing the different components of the lotus.

A range of other dyeing and antibacterial elements including alkaloids (pyridine, quinolin and stigmastan), flavonoids (phenyl and catechin), and anthraquinones were detected. In the lotus leaf extracts, 1,2-benzenedicarboxylic acid 3-nitro (C₈H₅NO₆) or pyridine (C₁₉H₁₄N₄O₂) (7.1%, matching: 96.2%) was detected at RT 81.172, and methoxyphenyl or anthracene (12.1%, matching: 98.0%) was detected at RT 91.812. In addition, a small amount of stigmastan (B-sitosterol glucopyranoside) was detected at RT 99.013 (0.9%, matching: 90.4%). A large amount of pentacosane or flavonoid was also detected at RT 100.313 and 100.216 (18.61%, matching: 90.3%). Lotus leaf extracts are a source of natural antioxidant with greater antioxidant effects than lotus seed. Moreover, the antibacterial effect of lotus leaf is proportional to the phenol content.¹⁷

In the lotus pot extracts, 1,2-benzenedicarboxylic acid 3-nitro (C₈H₅NO₆) or pyridine (C₁₉H₁₄N₄O₂) was detected at RT 81.273 (26.96%, matching: 94.2%), which was higher than that found in lotus leaves. In particular, a small amount of 2-naphthalenemethanol was detected in the lotus pots at RT 40.589 (2.6%, matching: 91.4%), which is assumed to have an insect-proof effect for preserving the seeds in the pot. Lotus has the similar antibacterial activity and insect-proof properties with other aromatic plants to protect itself from microorganisms and insects in wetlands as a water plant.¹⁸

In addition, a small amount of cyclotetra siloxane, octamethyl or di-phenyl trimethyl siloxy pentene (molecular weight 281, 296, matching: 90.7–94.9%), and quinolin (matching: 90.7%) were detected at RT 6.044, and a small amount of sulfuric acid extract (C₁₅H₃₂O₃S, 7.07%, matching: 91.0%) besides flavonoid was detected at both RT 103.245 and 106.254. Similarly, a small amount of special elements, such as silicon and sulfur, were detected at various levels in the lotus pots, but not in the lotus leaves or seeds.

In the lotus seeds, there were many nitrogen compounds with a high proportion of alkaloids. The peaks at approximately RT 55–58 accounted for 29.69% of the extracts and contained nitrogen. Of these, 1,2-ethanediamin, NNN'N'-tetraethyl (C₁₀H₂₄N₂, matching: 99.0%), ethyl amino (matching: 96.0%), pyridasine and pyrimidine (C₁₄H₂₂N₂O, matching: 91.4–95.1%), and tolycaine (C₁₅H₂₂N₂O₃, matching: 95.9%) were detected. These nitrogen compounds have high possibility to be transformed into ammonium hydroxide and quaternary ammonium compounds, which are known to have antimicrobial properties that disrupt cell membrane through the binding of their ammonium cations to anionic sites in the outer layer tissue of bacteria.¹⁹ A large amount of stigmastan (B-sitosterol glucopyranoside) was detected at RT 99.124 (5.59%, matching: 90.4%); the level was highest in the lotus seed extracts.

Dyeing property of lotus extracts

Color change in the processed cotton fabrics

We measured the color of treated cotton fabric, and Table 1 lists the lab values (brightness: black 0

\leftarrow \to

white 100), a (redness: red 60

\leftarrow \to

green –60) and b (yellowness: yellow 60

\leftarrow \to

blue –60) to highlight color changes in the cotton fabrics according to the dyeing process conditions. The lotus leaf and pots dyed the fabric green and orange, respectively. The lotus seed produced almost no color change for the peeled seeds had almost no color themselves.

Table 1.

Color changes: Lab values of cotton treated with lotus extracts

Fabrics treated	Condition		L	a	b	$Δ E$
Lotus leaf	None		94.52	−0.14	0.75
	Concentration	4%	85.53	−2.37	17.5	19.14
		6%	82.87	−1.68	18.73	21.48
		8%	79.98	−0.76	25.52	28.73
		10%	76.87	−0.31	28.44	32.84
		12%	74.32	0.27	31.08	36.44
	Time	30 min	84.54	−1.33	17.82	19.81
		60 min	85.53	−2.37	17.5	19.14
		90 min	86.16	−2.74	14.96	16.69
		120 min	86.14	−2.51	15.11	16.79
	Temperature	40℃	86.53	−2.8	15.52	17.00
		60℃	85.86	−2.53	14.3	16.26
		80℃	85.53	−2.37	17.5	19.14
		100℃	79.43	−2.05	22.62	26.64
Lotus pot	None		94.52	−0.14	0.75
	Concentration	4%	90.27	1.08	7.93	8.43
		6%	89.91	1.03	9.07	9.58
		8%	89.41	0.96	10.71	11.25
		10%	88	1.25	13.55	14.43
		12%	88.02	1.16	14.04	14.85
	Time	30 min	90.29	0.61	7.86	8.31
		60 min	90.27	1.08	7.93	8.43
		90 min	89.93	1.13	8.25	8.88
		120 min	88.87	1.77	8.76	9.99
	Temperature	40℃	90.72	0.45	7.16	7.48
		60℃	90.66	0.43	7.48	7.78
		80℃	90.27	1.08	7.93	8.43
		100℃	86.75	2.12	10.41	12.60
Lotus seed	None		94.52	−0.14	0.75
	Concentration	4%	93.72	−0.17	2.67	2.08
		6%	93.84	−0.12	2.93	2.28
		8%	93.96	−0.49	4.47	3.78
		10%	93.93	−0.57	4.83	4.14
		12%	93.65	−0.62	5.18	4.54
	Time	30 min	93.86	−0.31	2.83	2.19
		60 min	93.72	−0.17	2.67	2.08
		90 min	93.46	−0.53	3.23	2.73
		120 min	93.39	−0.07	3.01	2.53
	Temperature	40℃	94.07	−0.59	2.6	1.96
		60℃	94.05	−0.42	2.46	1.80
		80℃	93.72	−0.17	2.67	2.08
		100℃	93.63	−0.73	4.53	3.93

The dyed fabric with the lotus leaf extracts showed higher a and b values at higher processing concentrations (8–12%), lower a and b values according to processing time (30 → 120 min) causing green to yellow–green color, and higher a and b values at higher processing temperatures (100℃).

The fabric treated with the lotus pot extracts showed a higher b value at higher processing concentrations and processing temperatures, causing an orange color. The fabric dyed with the lotus seed extracts showed slightly higher b value at higher processing concentrations, causing a slight yellow color, but showed no significant difference.

When calculating the color difference, $Δ E$ , from the color of original fabrics using the L, a and b value, the color difference was the highest in the fabric treated with lotus leaf extract, followed in order by the pot extract treatment and the fabric seed extract treatment. The $Δ E$ value of the lotus leaf fabric changed from 19.1 to 36.4 when the processing concentration was increased from 4 to 12%, and the $Δ E$ value increased from 17.0 to 26.6 when the processing temperature was increased from 40 to 100℃. But the $Δ E$ value decreased from 19.8 to 16.8 with an increase in processing time from 30 to 120 minutes. Therefore, it is recommended to increase the treatment concentration and temperature and not dye the fabric for too long.

When examining color changes of the fabric treated with the lotus pots, the $Δ E$ value ranged from 8.4 to 14.9 with increasing processing concentration. The $Δ E$ value increased from 7.5 to 12.6 with increasing processing temperature and it also increased from 8.3 to 10.0 with increasing processing time but this change was not significant. The fabrics treated with lotus seeds showed the least significant change among the three treatment fabrics, that is, 2.1 → 4.5, 2.0 → 3.9 and 2.2 → 2.5 according to the processing concentration, temperature and processing time respectively.

Color uptake of treated cotton fabrics

Figure 2(a) shows the color ingredient uptake K/S value according to the concentration of lotus leaf, pot and seed extracts at the 400 nm wavelength. The extracts from the lotus leaves showed relatively steep increase, and lotus pots showed a steady increase, whereas the extracts from the lotus seeds showed almost no increase in K/S value. The color uptake of lotus pot fabric showed very low values (values under 1.0).

Figure 2.

Effect of treatment condition on the color uptake of cotton with lotus extracts: (a) concentration, (b) temperature, (c) processing time.

In Figure 2(b), the extracts from the lotus leaves and pots showed a gradual increase in color uptake at 40–100℃ with the highest uptake observed at 100℃, whereas the lotus seed extracts produced almost no increase in color uptake. Increasing the temperature from 80 to 100℃ produced a significant increase in color uptake for the leaf extract but not for the pot extract, suggesting that the pot extract has a lower optimal temperature.

In Figure 2(c), when processing the cotton fabrics with the lotus leaf extract, the uptake decreased slightly after 60 minutes. A longer processing time with the lotus leaves resulted in the discoloration of pale green chlorophyll. This suggests that the fabric should not be treated with lotus leaf extract for over 30 minutes.

When processing the cotton fabric with the lotus pot extract, the color uptake increased gradually with time, but the rate of increase between 30 and 120 minutes was very low. Therefore, 30–60 minutes would be the sufficient processing time for the lotus pot extract. The lotus seed extract showed almost no changes in color uptake according to the processing time.

So in order to get a high color ingredient uptake, it is recommended to treat fabric with high temperature, short processing time and high concentration of the extract. Concentration of the extract seems to be the most important factor, followed by the processing temperature, and the treatment time is of the least concern.

Measurement of the antibacterial activity of the extracted crude liquid

Table 2 lists the antibacterial activity of the crude liquid of 100% extract solution after evaporating the ethanol. A halo test to measure the formation of the zone of inhibition revealed a 3 mm zone for the two types of bacteria in the lotus pot extract, and a 2 mm zone for the lotus seed extract. This means that the lotus pots have better antibacterial activity than the lotus seeds. For the lotus leaves, the zone was 1 mm in Staphylococcus aureus and 3 mm in Klebsiella pneumoniae, suggesting better antibacterial activity against Klebsiella pneumoniae. The results show that the antibacterial activity of the crude liquid was highest in the lotus pot extracts. The lotus pots are assumed to have developed antimicrobial activity to protect the plant seeds. The pericarp of the lotus pot is capable of protecting the lotus fruits underground over hundreds of years.¹⁸

Table 2.

Zone of inhibition (unit: mm)—8 mm holes with one of 150 µl distilled water, two of 150 µl 100% solution

Also, a large amount of 1,2-benzenedicarboxylic acid 3-nitro (C₈H₅NO₆) or pyridine (C₁₉H₁₄N₄O₂) was detected in the lotus pot extracts. More alkaloids containing nitrogen, such as pyridine and quinolone, were detected in the lotus pots than in the lotus leaves. As lotus pot extracts contain various elements, such as silicon and sulfur, it is believed that lotus pot extract has antimicrobial insect-proof properties.

Measurement of the antibacterial degree of the treated cotton fabrics

Reduction of bacteria according to color uptake of fabric

Reduction of bacteria of leaf-extract fabric was correlated with the degree of color uptake. Flavonoid ingredients, also responsible for the strong color produced by the leaf extract, seemed to show a major antibacterial effect as well. Antibacterial activity of 80–89% reduction of bacterial growth will be referred to as slight antibacterial activity, 90–99.8% reduction as significant activity, and >99.9% reduction as strong activity. Significant antibacterial effect against Staphylococcus aureus was observed in fabric with the color uptake of 1.4, while significant antibacterial effect against Klebsiella pneumoniae was observed in fabric with the color uptake of 2.2 (Figure 3). Fabrics with similar color uptake, regardless of their treatment conditions, resulted in the same significant antibacterial activity (4%, 100℃ and 8%, 80℃).

Figure 3.

Antibacterial property according to color uptake with lotus.

Unlike the case of lotus leaf extract, the extracts of lotus pot and seed showed almost no relationship between color uptake and antibacterial activity. In the case of the lotus pot, even at the low color uptake of 0.5, the treated fabric showed significant antibacterial activity against both types of bacteria. This means the antibacterial effect appeared not only from the color uptake but also from the non-color ingredient of the lotus pot extract, which seem to be the minor ingredients in the extract such as chloride and sulfur. In the case of lotus seed, there was neither color uptake nor antibacterial activity.

Measurement of antibacterial degree according to the processing condition

The reduction ratio of Staphylococcus aureus and Klebsiella pneumonia of unprocessed cotton fabrics was 21.6% and 28.9%, respectively (Table 3). The lotus leaf extract showed a significant activity (90.9% reduction ratio of Staphylococcus aureus) at 8% processing concentration or higher. The lotus pot extract showed significant activity at all concentration conditions. The fabrics dyed with the lotus seed extract showed no antibacterial activity even with 12% extract concentration.

Table 3.

Antibacterial activities of cotton treated with lotus extracts according to the processing condition.

		Staphylococcus aureus			Klebsiella pneumonia
		Leaf	Pot	Seed	Leaf	Pot	Seed
0	21.6	21.6	21.6	28.9	28.9	28.9
Concentration (%)	4	24.5	91.2	27.6	28.3	63.1	40.3
	6	40.1	90.1	30.0	50.2	80.2	30.3
	8	90.9	98.7	26.1	45.3	97.3	30.5
	10	99.3	99.1	30.2	55.4	94.3	31.2
	12	99.6	99.7	30.3	99.7	99.4	31.0
Temperature (℃)	0	21.6	21.6	21.6	28.9	28.9	28.9
	40	20.2	99.3	20.2	20.3	94.5	30.2
	60	20.3	99.2	20.3	20.0	91.2	30.1
	80	24.5	91.2	27.6	28.3	63.1	40.3
	100	90.4	99.6	34.5	80.0	86.0	31.0
Time (min)	0	21.6	21.6	21.6	28.9	28.9	28.9
	30	20.3	98.7	20.3	20.1	75.6	20.0
	60	24.5	91.2	27.6	28.3	63.1	40.3
	90	30.4	90.2	40.4	30.2	63.1	50.2
	120	40.3	99.3	50.2	25.1	50.2	34.5

Regarding Klebsiella pneumonia, the conditions for dyeing fabrics with the lotus leaf extract resulted in >99.7%, significant activity, at a 12% concentration. The lotus pot extract showed a high reduction ratio, >97.3%, significant activity, at an 8% or higher concentration. Similar to the Staphylococcus aureus case, the lotus seed extract showed no antibacterial activity. Overall, the antibacterial activity was lower in Klebsiella pneumonia than in Staphylococcus aureus.

For the reduction ratio of Staphylococcus aureus according to the processing temperature, the fabrics treated with the lotus leaf extract showed significant antibacterial activity (90.4% reduction ratio) at 100℃, and those treated with the lotus pot extract showed significant activity (99.3%) even at low processing temperatures (40℃). On average, fabrics processed with lotus pot extracts had better antibacterial functionality than those processed with lotus leaf extracts. Fabrics treated with lotus seed extract showed no antibacterial activity even when the processing temperature was high.

For the bacteria reduction ratio of Klebsiella pneumonia, the fabrics dyed with the lotus leaf extract showed slight antibacterial activity (80%) at the highest temperature (100℃), and those treated with the lotus pot extract showed significant activity (91.2–94.5 %) at 40–60℃. At high temperature of 80–100℃, the activity of the lotus pot decreased unlike the case with Staphylococcus aureus. This indicates that low treatment temperature of the lotus pot produces better antibacterial activity against Klebsiella pneumonia. The fabrics treated with the lotus seed extract showed no antibacterial effect, even when processed at high temperatures.

For the reduction ratio of Staphylococcus aureus according to the processing time, the fabrics dyed with the lotus leaf extract showed no antibacterial activity at even 120 minutes, 80℃ and 4%, but those dyed with the lotus pot extract showed 90.2 % or higher reduction ratio, significant activity after being processed for more than 30 minutes. The fabrics dyed with the lotus seed extract showed no activity even when treated for a long time (120 minutes). For the reduction ratio of Klebsiella pneumonia according to the processing time, antibacterial activity was not observed at all.

Lotus pots showed the highest antibacterial property in both the extracted crude liquid and processed fabrics. This is a similar result to that reported in previous studies;²⁰ the order of antibacterial activity was lotus pot > lotus leaf > lotus seed for Staphylococcus aureus, and lotus leaf > lotus pot > lotus seed for the other types of bacteria. Although lotus seeds showed slight antibacterial activity in the crude liquid, they showed poor antibacterial degrees in the processed fabrics. This is because lotus seeds are composed mainly of protein components with low binding affinity with fibers. This suggests that other processing methods are needed. As lotus seeds are edible, they have a lesser likelihood of being applied to fabrics. Accordingly, lotus pots are suitable for achieving antibacterial activity, and lotus leaves are suitable for achieving both the green coloring and antibacterial property.

Conclusions

Antimicrobial finishing using renewable raw materials is definitely a preferred method, and medical plants such as the lotus plant have great value as antimicrobial active agents. This study focused on the potential use of the lotus plant in textile applications owing to its well-known pharmacological effects. The antibacterial functionality was examined by treating fabrics with the ethanolic extracts of lotus leaves, pots and seeds. In addition, the color change, dyeing property and color uptake of the fabrics were compared. The results are as follows:

GC-MS of the lotus plant extracts showed that the lotus leaves contained high concentrations of flavonoids and phenols; the lotus pots contained silicon, sulfur and a large amount of alkaloids; and lotus seeds contained high levels of protein, pyridazine, pyrimidine, alkaloids and vegetable hormone element stigmastan.

The color uptake on cotton fabrics was greater with higher concentrations of extracts. Fabric dyed with leaf extract showed the darkest color. The optimal dyeing conditions were 30 minutes at 100℃ for leaf and 30 minutes at 80℃ for pot extracts. Seed extracts had no optimal dyeing condition.

Fabric treated with lotus leaf extract showed green color from flavonoids along with slight antibacterial activity, and higher amount of color uptake was correlated with better antibacterial activity. In contrast, there was no relationship between color uptake and antibacterial activity among fabrics treated with pot extract, suggesting the presence of colorless antibacterial agents. Fabric treated with lotus seed extract showed no antibacterial effect unlike the crude extract.

Regarding the antibacterial degree of the treated fabric toward Staphylococcus aureus, the lotus leaf extract should be treated at concentrations of 8% or higher. If the concentration is lower than 8%, it should be processed at 100℃ to show significant antibacterial effect. On the other hand, the lotus pots had significant antibacterial activity at all concentrations.

Concentration of the extracts was the most important factor to consider during the antibacterial treatment process, followed by temperature and treatment time.

Footnotes

Funding

This research was supported by the National Research Foundation of Korea (grant number 2012-0002165) and an Inha University Research Grant.

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