Antioxidant and enzyme inhibitory potentials of phytochemicals isolated from Dioclea reflexa (Hook F.) stem: in-vitro and in-silico studies

Abstract

The objective of the study was to isolate and characterize phytochemicals from the stem extract of D. reflexa and investigate their biochemical activities. Five flavonoids together with two terpenoids, were isolated. Their structures were identified using 1D and 2D nuclear magnetic resonance (NMR) and mass spectroscopic techniques in combination with circular dichroism (CD) spectroscopy, as well as comparisons with published data. The in vitro reactive oxygen species scavenging potential of the compounds was investigated. The lipoxygenase and urease inhibitory potential of the compounds were tested using in vitro and in silico methods. Compound 1 and 2 exhibited potent antioxidant activity with lower IC50 values of 38.5 ± 0.25 and 39.5± 0.14 μM respectively compared with the standard used (BHA IC50 value = 39.5± 0.14) in DPPH assay. Compound 1 and 2 also exhibit good reducing ability and superoxide radical scavenging activity reflected by IC50 value 44.6 ± 0.30 and 48.5 ± 0.16 respectively compared with BHA (IC50 45.6 ± 0.54). Compound 2 and 3 showed significant inhibitory effect against urease with IC50 values 26.2 ± 0.29 μM and 36.5 ± 0.37 μM respectively, while compound 4 with IC50 value 33.3 ± 0.74 μM is the most active against lipoxygenase. All the seven compounds showed varying degrees of binding affinity against the targets with compounds 1–5 having the better docking score compared with the co-crystalized ligands of both lipoxygenase and urease. The density functional theory reveals the replicate of the transitional state between the compounds and their respective receptor and stability of the compounds was predicted from the energy gap (ELUMO – EHOMO). These compounds are potential drug against stomach ulcers, inflammation and oxidative stress associated diseases. It is also worth mentioning that the complete assignments of NMR data 1 and 2 were reported for the first time in this study.