Antioxidant Activity of Medicinal Plants Commonly Used to Treat Diabetes

Abstract

Plants are the most important source of bioactive compounds providing health benefits. To seek out the potential source of bioactive compounds such as polyphenols, flavonoids, anthocyanins and antioxidant of different medicinal plants that are commonly used to treat diabetes, methanolic extract of fourteen anti-diabetic plants or plant's part were studied. Among the extracts, Sonneratia apetala (seed) had the highest polyphenols (300 mg GAE/g) contents followed by Syzygium cumini (294 mg GAE/g) and Swertia chirata (183 mg GAE/g) whereas Asparagus racemosus had the lowest polyphenols (17.94 mg GAE/g) content followed by Coccinia indica (25.30 mg GAE/g) and Trigonella foenumgraecum (25.94 mg GAE/g). From the experiment it was seen that Swertia chirata contained the highest total flavonoids (77.92 mg CE/g extract) followed by Bacopa monnieri (59.95 mg CE/g extract), Syzygium cumini (31.70 mg CE/g extract) and Sonneratia apetala (seed) (30.63 mg CE/g extract). Total flavonoid was lowest in the extract of Swietenia mahagoni, and Trigonella foenumgraecum (0.974 mg CE/g extract). The highest amount of anthocyanin was found in Achyranthes aspera (4.65 µmol/g extract) followed by Sonneratia apetala (seed) (2.3 µmol/g extract), Ficus racemosa (bark) (1.75 µmol/g extract) and Coccinia indica (1.24 µmol/g extract) whereas it was lowest in case of Asparagus racemosus (0.09 µmol/g extract) followed by Swietenia mahagoni (0.15 µmol/g extract), Sonneratia apetala (pericarp) (0.25 µmol/g extract) and Gymnema sylvestre (0.26 µmol/g extract). Sonneratia apetala (seed) showed the most potent DPPH radical scavenging activity with an IC50 4.32 µg/ml followed by Syzygium cumini (6.25 µg/ml), Ficus racemosa (bark) (10.28 µg/ml) and Swertia chirata (12.61 µg/ml). Syzygium cumini and Sonneratia apetala (seed) both showed the powerful NO radical scavenging activity (at 400 µg/ml concentration) above 90% with an IC50 48.61 µg/ml and 49.41 µg/ml followed by Swertia chirata (110.55 µg/ml) and Ficus racemosa (bark) (161.76 µg/ml). At 200 µg/ml concentration, Sonneratia apetala (seed) was the highest absorbance (O.D-2.452) followed by Syzygium cumini (O.D-1.744), Ficus racemosa (O.D-1.513) and Swertia chirata (O.D-1.505). These extracts also showed promising total antioxidant capacity with Sonneratia apetala (seed) showed the highest antioxidant capacity (310.24 mg AAE/g; 280.77 mg GAE/g). This was followed by Syzygium cumini (207.82 mg AAE/g; 171.31 mg GAE/g) and Swertia chirata (155.03 mg AAE/g; 140.30 mg GAE/g). Total antioxidant capacity was lowest in the extract of Coccinia indica (14.15 mg AAE/g; 11.67.96 mg GAE/g). The results concluded that among the extracts Sonneratia apetala (seed), Syzygium cumini, Swertia chirata and Ficus racemosa (bark) are potential sources of bioactive compounds- polyphenols, flavonoids, anthocyanins, antioxidants and these medicinal plants therefore have activities beneficial to health.