Polyphenol fingerprinting and hypoglycemic attributes of optimized Cycas circinalis leaf extracts

Cycas circinalis leaves are used to treat diabetes mellitus in local medicinal systems without any scientifically proved information on their medicinal potential and phytochemicals. In this study, the total phenolic contents, total flavonoid contents, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging and inhibitory effects on α-glucosidase and α-amylase were determined for optimized hydroethanolic leaf extracts. Secondary metabolites were identified using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS/MS). In vivo studies on diabetic albino mice were also carried out to evaluate the impact of the most active extract on their blood glucose levels.

The 60% ethanolic extract showed the highest extract yield (209.70 ± 0.20 g kg^-1 ) and total phenolic (154.24 ± 3.28 mg gallic acid equivalent) and flavonoid (78.52 ± 1.65 mg rutin equivalent per gram dried extract) contents and exhibited the maximum DPPH scavenging activity (IC₅₀ = 59.68 ± 2.82 μg mL^-1 ). The IC₅₀ values for inhibition of α-glucosidase (58.42 ± 2.22 μg mL^-1 ) and α-amylase (74.11 ± 1.70 μg mL^-1 ) were also significant for the 60% ethanolic extract. The untargeted UHPLC-QTOF-MS/MS-based metabolite profiling confirmed the presence of iridoid glucoside, gibberellin A4, O-β-d-glucosyl-4-hydroxy-cinnamate, 3-methoxy-2-phyenyl-4H-furo[2,3-h]chromen-4-one, kaempferol, withaferin A, amentoflavone, quercitin-3-O-(6″-malonyl glucoside), ellagic acid, and gallic acid. Plant extract at a dose of 500 mg kg^-1 body weight reduced the blood glucose level by a considerable extent and also improved the lipid profile of diabetic mice after a 28-day trial.

The findings revealed the medicinal potential of C. circinalis leaves to treat diabetes mellitus and provided the nutraceutical leads for functional food development. © 2020 Society of Chemical Industry.