Md. Rakib Hasan*, Nizam Uddin, Md. Monir Hossain, Sabiha Begum, Arjyabrata Sarker, D. M. Jakaria, Md. Emtiaz Yousuf, Md. Sohel Rana
Galphimia gracilis Bartl. (Family- Malpighiaceae) is known as gold shower and available almost everywhere in Bangladesh. This plant has some medicinal properties and is used as a source of vitamins. The current study was designed to evaluate in vitro antioxidant, brine shrimp lethality and antimicrobial activities of methanol (GSM), ethyl-acetate (GSEA) and petroleum ether (GSPE) extracts of G. gracilis stem. In vitro antioxidant activity of the extracts were studied using DPPH radical scavenging assay, NO scavenging assay, total phenol, total flavonoid content, total antioxidant capacity, total tannin content and lipid peroxidation in human erythrocyte cell assays. Lethality bioassay was performed on Artemia salina Leach nauplii. Antimicrobial activity was investigated by disc diffusion technique. Presence of alkaloids, carbohydrates, flavonoids, steroids, terpenoids, tannins, saponins and glycosides were identified in the extracts. Ethyl-acetate extract showed highest activities in DPPH (IC50 22.82±0.172 μg/ml), NO (IC50 72.886±0.394 μg/ml) and total antioxidant assay (210.86±3.436 mg/gm Ascorbic Acid Equivalent). Methanol extract showed highest content in total phenol (972.02±4.56 mg/g Gallic Acid Equivalent), total flavonoid (135.98±1.103 mg/g Quercetin Equivalent) and total tannin content assays (111.454±1.462 mg/g Tannic Acid Equivalent). Ethyl acetate extract showed promising reducing capacity than other extracts in cupric reducing (correlation coefficient r= 0.99 and P<0.01) and reducing power capacity assays (r= 0.99 and P<0.001). Besides, it showed dose dependent activity in both assays. In brine shrimp lethality bioassay, methanol extract was found to be more potent than other extracts (LC50=58.583 μg/ml, χ2=170.967, P<0.001). In disk diffusion technique methanol extract showed highest zone of inhibition against maximum number of microorganisms Staphylococcus aureus, Salmonella typhi, Salmonella abony and Pseudomonas aeruginosa (6.75±0.353 mm). The present findings suggest that the stem extracts of G. gracilis can be used as a source of potential candidates for lead compounds.
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