α -Glucosidase and α -amylase inhibitory potential of main compounds and drug candidates from Elaeagnus rhamnoides (L.) A. Nelson

Elaeagnus rhamnoides (L.) A. Nelson (synonym: Hippophae rhamnoides ) (Elaeagnaceae) is an important plant with multiple usages. The current study was laid on discovering the phytochemical profiling of E. rhamnoides leaves through antihyperglycemic and antioxidant effects. The ethyl acetate (IC 50 = 46.89 ± 2.18 µg/mL) and n -butanol extracts (IC 50 = 51.33 ± 2.53 µg/mL) possessed potent inhibitory activity against α -glucosidase enzyme as compared with standard compound, acarbose (IC 50 = 4212.62 ± 130.00 µg/mL). Seven compounds were isolated, and their structure was determined by 1D- and 2D-NMR. Isorhamnetin-3- O - β - d -glucopyranosyl-7- O - α - l -rhamnopyranoside (1) , isorhamnetin-7- O - α - l -rhamnopyranoside (2) , isoquercitrin (3) , narcissin (4) , isorhamnetin-3- O - β - d -glucopyranoside (5) , arjunglucoside I (6) , and casuarinin (7) were isolated from n -butanol extract. All isolated compounds, especially arjunglucoside I (IC 50 = 1074 ± 32 µM) and casuarinin (IC 50 = 21 ± 2 µM), showed higher α -glucosidase inhibitory activity than acarbose (IC 50 = 6561 ± 207 µM). Casuarinin displayed powerful scavenging activity against to both ABTS radical with 2 ± 1 µM IC 50 value and DPPH radical with 14 ± 1 µM IC 50 value while IC 50 values of trolox and α -tocopherol were 31 ± 1 and 50 ± 1 µM against ABTS radical, and 67 ± 2 and 95 ± 3 µM against DPPH radical, respectively. Arjunglucoside I was isolated for first time from this species and Elaeagnaceae family. Preparations prepared from E. rhamnoides leaf extracts standardized via casuarinin and arjunglucoside I could be potential phytotherapeutics for diabetes mellitus. Graphic abstract