Evaluation of Antioxidant, Brine Shrimp Lethality and Antimicrobial Activities of Galphimia gracilis Bartl. Leaf Extracts Using in vitro Assay Models

Aims: Galphimia gracilis Bartl. (Family- Malpighiaceae) is known as gold shower or shower of gold. The current study was designed to evaluate in vitro antioxidant, brine shrimp lethality and antimicrobial activities of methanol, ethyl-acetate and petroleum ether extracts of G. gracilis leaf.

Study Design: Phytochemical screening, in vitro antioxidant, brine shrimp lethality and antimicrobial activities.

Place and Duration of Study: Department of Pharmacy, Jahangirnagar University, Savar, Dhaka-1342. The studies were carried out from November 2013 to February 2014.

Methodology: In vitro antioxidant activity of the extracts were studied using DPPH radical scavenging assay, Nitric oxide (NO) scavenging assay, total phenol content, total flavonoid content, total antioxidant content, 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.

Results: Presence of alkaloids, carbohydrates, flavonoids, steroids, terpenoids, tannins, saponins and glycosides were identified in the extracts. Ethyl-acetate extract (GLEA) showed highest activities in DPPH (IC50 of 21.70±0.51 µg/ml), NO (IC50 of 35.50±0.30 µg/ml), lipid peroxidation in human erythrocyte cells (IC50 of 10.38±0.34 µg/ml), total phenol (934.04±3.21 mg/g Gallic Acid Equivalent), total flavonoid (236.88±2.66 mg/g Quercetin Equivalent) and total antioxidant capacity assays (978.58±1.66 mg/g Ascorbic Acid Equivalent) among three different extracts. Methanol extract (GLM) showed promising reducing capacity than other extracts in cupric reducing (correlation coefficient, r= 0.95 and P<0.05) and reducing power capacity assays (r= 0.993 and P<0.001). Besides, it showed dose dependent activity in both assays. Methanol extract showed maximum content in total tannin assay (89.34±1.37 mg/g Tannic Acid Equivalent). In brine shrimp lethality bioassay, methanol extract was found to be more potent than other extracts (LC50=64.46 µg/ml, χ2=39.87, P<0.0001). In disk diffusion technique, all the extracts showed poor activity.

Conclusion: The present findings suggest that leaf extracts of G. gracilis have promising antioxidant and cytotoxic activities. Moreover, the extracts can be used as potential candidates for lead compounds.