This study evaluated the in vitro antioxidative activity of Khaya senegalensis extracts and inhibitory effects of some solvent fractions on α-glucosidase and α-amylase activities. The stem bark, root and leaf samples of the plant were sequentially extracted with ethyl acetate, ethanol and water and then tested for antioxidative activity. Our findings revealed that the ethanolic extract of the root had the highest antioxidative activity. Solvent-solvent fractionation of the root ethanolic extract yielded a butanol fraction that showed higher antioxidative activity than other fractions. Furthermore, the butanol fraction had significantly higher (p < 0.05) α-glucosidase and α-amylase inhibitory activities with IC ₅₀ values of 2.89 ± 0.46 and 97.51 ± 5.72 μg mL ^-1 , respectively. Enzyme kinetic studies indicated that the butanol fraction is a non-competitive inhibitor for α-glucosidase with an inhibition binding constant K _i of 1.30 μg mL ^-1 and a competitive inhibitor of α-amylase with a K _i of 7.50 μg mL ^-1 . GC-MS analysis revealed that the butanol fraction contained two chromones, p-anilinophenol and 3-ethyl-5-(3- ethyl-(3H)-benzothiazol-2-ylidene)-2-(p-tolylvinylamino)- 4-thiazolidinone. Data obtained in the study suggest that the butanol fraction derived from the ethanolic extract of K. senegalensis root possessed excellent antioxidative as well as α-glucosidase and a-amylase inhibitory activities while chromones and/or p-anilinophenol could be the main bioactive compounds responsible for the observed activities.

Antibacterial and Anti-Biofilm Activity of Flavonoids and Triterpenes Isolated from The Extracts of Ficus Sansibarica Warb. Subsp. Sansibarica (Moraceae) Extracts

Context: The use of Aframomum melegueta K. Schum. (Zingiberaceae) fruit for treatment of diabetes has recently been established in Nigeria. However, compounds responsible for the antidiabetic action have not been identified. Objective: The present study carried out the bioassay-guided isolation of possible bioactive compounds responsible for the antidiabetic action of A. melegueta fruit. Materials and methods: The A. melegueta fruit was sequentially extracted using ethyl acetate (EtOAc), ethanol and water, and the most active extract (EtOAc) was subjected to column chromatography on a silica gel column using solvent gradient systems of hexane (HEX):EtOAc and EtOAc:MeOH and the isolation of compounds was guided by α-glycosidase and α-amylase inhibitory activities at various concentrations (30–240 μg/mL). Results: According to the results, 3 arylalkanes, 6-paradol (1), 6-shogaol (2) and 6-gingerol (3) and a pentacyclic triterpene, oleanolic acid (4) were isolated from A. melegueta fruit. All the compounds exhibited inhibitory effects against α-amylase and α-glucosidase. 6-Gingerol (3) and oleanolic acid (4) showed higher inhibitory activity against α-amylase (IC₅₀: 6-gingerol: 81.78 ± 7.79 μM; oleanolic acid: 91.72 ± 1.63 μM) and α-glucosidase (IC₅₀: 6-gingerol: 21.55 ± 0.45 μM; oleanolic acid: 17.35 ± 0.88 μM) compared to the standard drug, acarbose and other isolated compounds. The kinetics of the enzyme action of the compounds showed a noncompetitive mode of inhibition. Conclusion: The data of this study suggest that the 6-gingerol (3) and oleanolic acid (4) showed higher α-amylase and α-glucosidase inhibitory action and therefore could be responsible for the antidiabetic activity of A. melegueta fruit.

The progression of secondary complications in type 2 diabetes (T2D) has been linked to oxidative stress caused by hyperglycemia. Therefore, the control of hyperglycemia is the main target in the treatment of diabetes. The present study investigated the scavenging and ameliorative potentials of different fractions of Azadirachta indica (A. indica) ethanol stem bark extract in Fe²⁺-induced oxidative injury in hepatic tissue as well as their ability to inhibit enzymes linked to diabetes and in enhancing muscle glucose uptake via some in vitro and ex vivo experimental models. The results revealed that the butanol fraction of the extract showed a significantly (p < 0.05) higher DPPH scavenging activity than the other fractions (IC₅₀ 0.0154 μg/mL), while the aqueous fraction showed the highest FRAP activity (IC₅₀ 25.32 μg/mL). Although all the fractions ameliorated Fe²⁺-induced oxidative injury in hepatic tissue by significantly reducing malondialdehyde (MDA) concentration in a dose dependent manner, the butanol fraction showed the highest activity in this regard. In addition, the activities of catalase and superoxide dismutase (SOD) were significantly improved by the butanol and dichloromethane fractions. Butanol and ethyl acetate fractions showed the highest inhibitory effect on α-glucosidase (IC₅₀ 0.23 μg/mL) and α-amylase (IC₅₀ 14.79 μg/mL) activities, respectively. Although all the fractions significantly improved glucose uptake in psoas muscle with or without insulin, the butanol fraction showed the highest activity (GU₅₀ 6.22 μg/mL) in this regard. Gas chromatography-mass spectroscopy (GC-MS) analysis of the fractions revealed the presence of sistosterol, stigmasterol, campestrol, squalene, nimbiol among others. Molecular docking of some of these compounds with AMP-activated protein kinase (α-AMPK), α-amylase and α-glucosidase showed a positive interaction. These results suggest that the butanol and ethyl acetate fractions of A. indica may have bioactive compounds with antidiabetic potentials.