BIOLOGICAL ACTIVITIES OF POLYGONUM FLACCIDUM

BIOLOGICAL ACTIVITIES OF POLYGONUM FLACCIDUM

Pritesh Ranjan Dash ¹, Md. Sohel Rana ^{* 1} and Md. Hossain Sohrab ²

Department of Pharmacy, Jahangirnagar University ¹, Savar, Dhaka, Bangladesh.

Chemical Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR) Laboratories Dhaka ², Dhaka - 1205, Bangladesh.

ABSTRACT: Polygonum flaccidum (Polygonaceae) is an annual herb widely distributed in Bangladesh, India, Bhutan, Sri Lanka, and Afghanistan. Objectives of the present study were to determine antioxidant, anthelmintic, cytotoxic, insecticidal and antibacterial activities of methanol extract of P. flaccidum. Antioxidant activity in terms of free radical scavenging ability was determined by DPPH free radical scavenging assay. Cytotoxic activity was performed by brine shrimp (Artemia salina) lethality bioassay. Anthelmintic efficacy was determined using adult Bangladeshi earthworm. Insecticidal activity was tested against rice weevil Sitophilus oryzae. Antibacterial activity was tested by the disc diffusion method. The extract exhibited significant antioxidant activity by scavenging DPPH free radical. The IC₅₀ value of the extract displayed 4.91μg/ml while standard ascorbic acid showed 2.69 μg/ml. The extract exhibited potent anthelmintic activity by causing paralysis (30 min) and death (45 min) of worms and the effect was found to be dose-dependent. In an insecticidal study, the lethal effect of methanol extract on Sitophilus oryzae was found to be dose-dependent manner. In cytotoxicity study, LC₅₀ value of the methanol extract was 1.5 μg/ml while the LC₅₀ value of vincristine sulfate was 0.52 μg/ml. On the other hand, the methanol extract also showed remarkable antibacterial activity against both the gram positive and negative bacteria but inactive against fungi. Further studies on isolation of constituents and their bio-efficacies in-vitro and in-vivo are under investigation.

Polygonum flaccidum, Antioxidant, Anthelmintic, Cytotoxic, Insecticidal and Antibacterial activities

INTRODUCTION: Polygonum flaccidum (Commonly known as Lalbishkatali) a Bangladeshi annual herb, is well known for it is analgesic, anti-inflammatory, diuretic, purgative and insecticidal properties ^{1, 2}. This plant has also been used traditionally to treat snake-bites.

Previous phytochemical studies on this species revealed the presence of epoxides, flavonoids, steroids and terpenoids ^{1, 3}. Since, this plant has important medicinal properties, the present study has been undertaken and we, herein, report the antioxidant, anthelmintic and cytotoxic, properties of P. flaccidum for the first time, and we also report the insecticidal and antibacterial activities. Aerial parts of Polygonum flaccidum was collected from the local area of Savar, Dhaka during January 2014.

The collected plant was then identified by the taxonomist of Jahangirnagar University Herbarium, Savar, Dhaka and a voucher specimen (DACB: 39,317) has been deposited for future reference.

The powdered aerial parts (1 kg) of P.flaccidum were extracted by cold extraction method with 6 L of methanol for 7 days at room temperature with occasional stirring. The extract was then filtered and evaporated on a rotary evaporator under reduced pressure to obtain 48.59 gm extract which was used for biological screening.

The antioxidant activity (free radical scavenging activity) of the extract on the stable radical 1, 1-diphenyl- 2-picrylhydrazyl (DPPH) was determined by following standard protocol developed by Brand-Williams ^{4, 5}. Then % inhibitions were plotted against respective concentrations used, and from the graph, IC₅₀ was calculated by using Ascorbic acid (AA), a potent antioxidant as a positive control. The experiments were carried out in triplicate and the results have been shown as mean ± SEM (standard error of the mean).

Adult Bangladeshi earthworms (Pheretima Posthuma) were used to assess the anthelmintic effect of the extract. The worms were washed using normal saline (0.85%) to remove extraneous matter. Six worms of equal size (6 cm long) were transferred into normal saline (0.9% NaCl) containing standard drug (Pyrantel pamoate 10 mg/kg) and different concentrations of extract (25, 50 and 100 mg/ml). The time taken for paralysis of worms was noted when no movement was observed (except when the worms were shaken vigorously). The death time was taken when worms failed to exhibit movement on shaking vigorously or on dipping in slightly hot water (50°C). Normal saline served as control ⁶.

The insecticidal effect of different concentrations of extract (5, 10, 20, 40, 50, 60, 70 and 80 mg/ml) was tested against Sitophilus oryzae also called rice weevil because of its habitat, we collected rice weevil from old rice godown, Dhaka. Briefly, ten insects were placed in beakers containing extract. A control was kept without adding extract. The insecticidal effect of the extract was determined by counting the number of a dead insect after 12 and 24 h. Dead insects were identified by no movement after probing with a needle in a siphon or cervical region. The experiment was repeated triplicate, and average mortality (%) was noted ^{7, 8}.

For cytotoxicity screening, crude methanol extract was dissolved in DMSO ^{9, 10}. The test samples were then applied against Artemia salina in a 1- day in vitro assay. The experiments were carried out in triplicate using vincristine sulfate as standard, and the results have been shown as mean ± SEM (standard error of the mean).

The antibacterial activity of the extract was determined by the disc diffusion method ^11,12 against 2 gram-positive bacteria, 2 gram-negative bacteria, and 2 fungal strains. The organisms were collected as pure cultures from the Institute of Nutrition and Food Sciences (INFS), University of Dhaka. The experiments were carried out in triplicate using ciprofloxacin as standard and the results have been shown as mean ± SEM (standard error of the mean).

Statistical differences between extract activities were determined using ANOVA followed by Least Significant Difference (LSD) testing. Data were expressed as mean ± SEM (standard error of the mean). Differences were considered statistically significant when p<0.5.

The methanol extract of P. flaccidum exhibited significant antioxidant activity with the IC₅₀ value of 4.91 μg/ml against DPPH free radical while standard ascorbic acid showed 2.69 μg/ml Table 1.

TABLE 1: IC₅₀ VALUES OF STANDARD AND METHANOL EXTRACT OF P. FLACCIDUM IN DPPH ASSAY

PF= Polygonum flaccidum, AA= Ascorbic Acid

The potent anthelmintic activity was observed at the concentration of 100 mg/ml Table 2. At this concentration, the time required for paralysis and death of earthworms was only 30 and 45 minutes respectively whereas time taken for paralysis and death by the standard drug Pyrantel pamoate (10 mg/ml) was 26 and 35 min respectively.

TABLE 2: ANTHELMINTIC ACTIVITY OF P.FLACCIDUM

The methanol extract of P. flaccidum exhibited potent insecticidal activity with the IC₅₀ value of 66.31 μg/ml and 6.43 μg/ml against Sitophilus oryzae after 12 h and 24 h respectively Table 3.

TABLE 3: LC₅₀ VALUES OF METHANOL EXTRACT OF P. FLACCIDUM IN INSECTICIDAL ACTIVITY AFTER 12 h AND 24 h

Table 4 shows the results of the brine shrimp lethality assay after 24 hr exposure to the samples and the positive control vincristine sulfate. The positive control, compared with the negative control (DMSO) was lethal, depicting significant mortality to the shrimp. The median lethal concentration (LC₅₀) of the test samples after 24 hr was obtained by a plot of percentage of the shrimps killed against the logarithm of the sample concentration (toxicant concentration) and the best-fit line was obtained from the graph using regression analysis. The LC₅₀ value of methanol extract of P. flaccidum was 0.15μg/ml.

TABLE 4: RESULTS OF CYTOTOXICITY SCREENING OF P. FLACCIDUM

VS = Vincristine sulfate, PF= Polygonum flaccidum

The methanol extract of P. flaccidum was tested for antibacterial and antifungal activities against a number of gram positive and gram negative bacteria as well as some fungi. The extract showed the remarkable antibacterial activity against both the gram positive and negative bacteria but inactive against fungi.

TABLE 5: ANTIMICROBIAL ACTIVITY OF P. FLACCIDUM

PF = Polygonum flaccidum, Cipro = Ciprofloxacin, 0 =No Zone of inhibition

CONCLUSION: By the above biological screenings and folk medicinal uses, it can be concluded that this plant has significant medicinal properties. It is also clearly evident from the above findings that the whole plant of Polygonum flaccidum has high antioxidant, anthelmintic, cytotoxic, insecticidal potential and remarkable antibacterial activities. Therefore, the plant is a good candidate for further studies to isolate the bioactive principles.

ACKNOWLEDGEMENT: Nil

CONFLICT OF INTEREST: Nil

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    How to cite this article:

    Dash PR, Rana MS and Sohrab MH: Biological Activities of Polygonum Flaccidum. Int J Pharmacognosy 2016; 3(5): 217-20. doi: 10.13040/IJPSR.0975-8232.3(5).217-20.

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