In Vitro Antidiabetic, Antioxidant, and Cytotoxic Evaluation of Honeybush Tea (Cyclopia genistoides) Extracts

Abstract

Background. This study evaluated in vitro antidiabetic and antioxidant properties of different extracts (n-hexane, dichloromethane (DCM), and 70% ethanol) of honeybush tea (Cyclopia genistoides). Over a period of 28 days, antiprotein glycation was evaluated and some antidiabetic indicators (α-amylase, α-glucosidase, and pancreatic lipase inhibitory effects) and antioxidant activities (DPPH, ABTS, hydroxyl radical, metal ion chelating, and reducing power) for each of the crude extracts were also investigated. The results showed that all of the tested C. genistoides extracts had strong α-amylase and lipase inhibitory activity in a concentration-dependent manner with IC50 values from 0.018 μg/ml (DCM extract) to 9.93 μg/ml (n-hexane extract), respectively. The extracts also displayed inhibitory effects on protein glycation between the 14th and 28th days. The DCM and ethanolic extracts further exhibited strong antioxidant activities as they effectively scavenged most of the radicals tested, with IC50 values ranging from 0.014–0.048 mg/ml to 0.019–0.043 mg/ml. Two hundred and seventy-four chemical constituents had been identified by GC-MS, with the n-hexane extract having the highest number of peaks (127) followed by the DCM extract (107). Six compounds were identified across all the following three extracts: decane (RT: 6.4), undecane (RT: 7.7), dodecane (RT: 9.00), phytol (RT: 21.32), heptadecanoic acid, 9-methyl, methyl ester (RT: 21.65), and 9-octadecenamide (RT: 24.30). The cytotoxicity of the extracts against C3A cell lines was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay, which demonstrated that honeybush tea had a toxicity effect ranging from 66.3–88.4 μg/ml on C3A cell lines. The results showed that honeybush has antioxidant and antidiabetic activities, which could be partially attributed to the phytochemical compounds identified within the extracts.