Abstract

• Nephelium lappaceum L. (Sapindaceae) popularly known as Kyet-mauk in Myanmar which is one of the traditional medicinal plant. So, N. lappaceum (Kyet-mauk) seeds were chosen for this research work. The present research work was designated to evaluate the antioxidant, antidiabetic, antimicrobial and cytotoxic activities of N. lappaceum seed. The preliminary phytochemical investigation by test tube method revealed the presence of alkaloids, α–amino acids, carbohydrates, flavonoids, glycosides, organic acids, phenolic compounds, reducing sugars, saponins, starch, tannins and terpenoids. Cyanogenic glycosides and steroids were not found in N. lappaceum seed. Investigation on nutrients (moisture, ash, fat, protein, fiber and carbohydrate) of N. lappaceum seed has been carried out by AOAC method. An energy value (Kyet-mauk) seed was found to be 430.07 kcal/100 g on the basis of dried sample. The mineral contents: K, Ca, Fe, Zn, Mn, Cu, and Rb were relatively observed by EDXRF spectroscopy. Among them, potassium content of the sample was the highest (49.528 %). In the screening of the antioxidant activity by DPPH method, IC50 values of ethanol and watery extracts were found to be 16.34 μg/mL and 17.31 μg/mL, respectively. In vitro α-amylase inhibitory activity of ethanol and watery extracts was investigated by using the starch-iodine method. The percent inhibition of α-amylase activity of ethanol extract (IC50 = 80.58 μg/mL) and watery extract (IC50 = 178.86 μg/mL) indicated the superiority of ethanol extract over watery extract. The total phenol contents (TPC) of ethanol and watery extracts of N. lappaceum seed were determined by FCR method. The TPC contents of ethanol and watery extracts were respectively observed to be (79.88 ± 2.86 µg GAE/mg) and (30.73 ± 7.65 µg GAE/mg). The antimicrobial activities of the various crude extracts (petether, acetyl acetate, ethanol and watery extracts) of N. lappaceum seed sample were determined against six strains of microorganisms by agar well diffusion method. The ethanol extract showed the antimicrobial activity with the inhibition zone diameters range 10 ~ 14 mm against six microorganisms such as B. subtilis, S. aureus, P. aeruginosa, B. pumilus, C. albicans and E. coli. The cytotoxicity of ethanol and watery extracts of N. lappaceum seed were evaluated by brine shrimp cytotoxicity bioassay. The LD50 values of ethanol and watery extracts were LD50 > 1000 μg /mL.