Screening of Antioxidant and α-Glucosidase Inhibitory Activities of Indian Medicinal Plants

Abstract

Background and objective: Chronic diseases are associated with low-grade inflammation and oxidative damage. Traditional medicines have been used to manage these disorders due to their high polyphenol content and potent antioxidant activity. We evaluated the in-vitro anti-diabetic and antioxidant potential of extracts of several medicinal plants namely, Mangifera indica, Terminalia arjuna, Moringa oleifera, Albizia lebbeck, Terminalia chebula and Hippophae rhamnoides. Methods: Total polyphenol, flavonoid, and saponin contents were estimated by standard methods. Antioxidant activity was measured using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. The anti-diabetic potential was evaluated using in-vitro α-glucosidase inhibition assay. Background and objective: Chronic diseases are associated with low-grade inflammation and oxidative damage. Traditional medicines have been used to manage these disorders due to their high polyphenol content and potent antioxidant activity. We evaluated the in-vitro anti-diabetic and antioxidant potential of extracts of several medicinal plants namely, Mangifera indica, Terminalia arjuna, Moringa oleifera, Albizia lebbeck, Terminalia chebula and Hippophae rhamnoides. Methods: Total polyphenol, flavonoid, and saponin contents were estimated by standard methods. Antioxidant activity was measured using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. The anti-diabetic potential was evaluated using in-vitro α-glucosidase inhibition assay. Results: Terminalia chebula was found to be the richest in both polyphenols (566.5±21.9 µg Gallic acid equivalents/mg of dry weight) and flavonoids (190.67±10.78 quercetin equivalents/mg of dry weight). Extract of Terminalia arjuna was the richest source of saponins (171.92±12.48 μg saponin equivalents/mg of dry weight). All plant extracts showed potent anti-oxidant activity as reflected by their IC50 values in DPPH assay, with Albizia lebbeck (IC50 = 1.35 µg/ml) being the most potent. All plant extracts also showed potent anti-diabetic activity as inferred from their ability to inhibit αglucosidase, the principal enzyme involved in the metabolism of dietary carbohydrates in the intestine. It was observed that all tested extracts were more potent (IC50 2.53 to 227 µg/ml) in comparison to the standard α-glucosidase inhibitor Acarbose (IC50=2.7 mg/ml). Conclusions: The plant extracts of Mangifera indica, Terminalia arjuna, Moringa oleifera, Albizia lebbeck, Terminalia chebula,and Hippophae rhamnoides possess potent antioxidant and α-glucosidase inhibitory potential and can aid in the management of postprandial hyperglycemia and oxidative damage. Conclusions: The plant extracts of Mangifera indica, Terminalia arjuna, Moringa oleifera, Albizia lebbeck, Terminalia chebula,and Hippophae rhamnoides possess potent antioxidant and α-glucosidase inhibitory potential and can aid in the management of postprandial hyperglycemia and oxidative damage.

Flavonoids as Human Intestinal α-Glucosidase Inhibitors

“…Quercetin is a potent inhibitor of intestinal GLUT2, substantially reducing glucose absorption [69]. Quercetin has repeatedly been reported to inhibit yeast α-glucosidases more so than acarbose [42,50,[70][71][72]. In contrast, for rat maltase and sucrase, it was shown to be weaker than acarbose (IC 50 = 281.2 µM for maltase, IC 50 > 400 µM for sucrase) [52], similar to the data reported here.…”

“…At the molecular level, the binding between hydroxyls in ring A, B or C of flavonoids to the active sites of α-glucosidases leads to structural changes in the enzyme evidenced by several docking studies with yeast α-glucosidase [20,55,72,79]. The inhibitory activity of flavonoids was concluded to be in the decreasing order of anthocyanidin ≥ isoflavone ≥ flavonol ≥ flavone ≥ flavonone ≥ flavan-3-ol [50], indicating the crucial role of A ring hydroxylation for potent α-glucosidases inhibition [80].…”

Reversal of Increase in Intestinal Permeability by Mangifera indica Seed Kernel Extract in High-Fat Diet-Induced Obese Mice

“…The 50% ethanolic extract of Mangifera indica (MESK) was characterized using various colorimetric and analytical methods, and the results are published elsewhere [ 21 ]. In brief, the total polyphenol, flavonoid, and saponin content of MESK were 187.9 ± 14.5 µg/mg, 160.4 ± 6.2 µg/mg, and 8.3 ± 0.15 µg/mg, respectively.…”

“…In brief, the total polyphenol, flavonoid, and saponin content of MESK were 187.9 ± 14.5 µg/mg, 160.4 ± 6.2 µg/mg, and 8.3 ± 0.15 µg/mg, respectively. In vitro studies suggested that MESK was a strong inhibitor of α-glucosidase and possesses significant antioxidant properties in 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging assay [ 21 ]. We tentatively identified Gallic acid, Ethyl gallate, Cinnamic acid, and Catechin as some of the phytoconstituents in MESK using mass spectroscopy [ 21 ].…”

“…In vitro studies suggested that MESK was a strong inhibitor of α-glucosidase and possesses significant antioxidant properties in 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging assay [ 21 ]. We tentatively identified Gallic acid, Ethyl gallate, Cinnamic acid, and Catechin as some of the phytoconstituents in MESK using mass spectroscopy [ 21 ]. HPLC analysis confirmed that Gallic acid is one of the major phytoconstituents of MESK ( Figure 3 ).…”