Antidiabetic Activity of Terminalia sericea Constituents

Abstract

Diabetes mellitus is an endocrine disorder that affects more than 100 million people worldwide. South African plants namely Terminalia sericea, Euclea natalensis, Warbugia salutaris, Aloe ferox, Artemisia afra, Sclerocarya birrea, Spirostachys africana and Psidium guajava were investigated for their in vitro α-glucosidase and α-amylase properties, and antioxidant activities. Terminalia sericea stem bark extract showed the best results against α-glucosidase and α-amylase enzymes. Bioassay-guided fractionation of an acetone extract of T. sericea stem bark led to the isolation of four known compounds namely β-sitosterol (1), β-sitosterol-3-acetate (2), lupeol (3), and stigma-4-ene-3-one (4), in addition to two inseparable sets of mixtures of isomers [epicatechin-catechin (M1), and gallocatechin-epigallocatechin (M2). 1 and 3 showed the best inhibitory activity on α-glucosidase (IC 50 :54.5 and 66.5 µM). Bio-evaluation of the inhibitory activity of the purified compounds on α-amylase showed that 3 and 1 exhibited IC 50 values of 140.7 and 216.02 µM, respectively against α-amylase. Compounds 2, M1, 3 and M2 were found to be non-toxic to Vero cells. This study is the first to report -glucosidase and -amylase activity of M1, M2, 2 and 4 isolated from T. sericea, which validated the traditional use of the bark of T. sericea for diabetes in South Africa.

Review of Ethnomedicinal Uses, Phytochemistry and Pharmacological Properties of Euclea natalensis A.DC.

“…Extracts from Euclea natalensis possess a wide spectrum of pharmacological properties, including antibacterial [ 25 , 35 , 40 , 50 , 52 , 61 , 62 , 63 ], antimycobacterial [ 17 , 39 , 52 , 54 , 55 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ], antifungal [ 51 , 57 ], antiviral [ 18 , 71 ], antidiabetic [ 72 ], antioxidant [ 67 , 72 ], antiplasmodial [ 73 ], larvicidal [ 74 ], antischistosomal [ 75 ], molluscicidal [ 76 ], dentin permeability [ 77 , 78 ], hepatoprotective [ 79 ], cytotoxicity [ 17 , 18 , 35 , 67 , 80 ] and toxicity [ 19 ] activities as outlined below. Some of the documented pharmacological properties of crude extracts and compounds isolated from the species may be responsible for the ethnomedicinal uses of the species indicated in Table 1 .…”

“…Nkobole et al [ 72 ] evaluated antidiabetic activities of acetone root extracts of E. natalensis by assessing in vitro α-glucosidase and α-amylase enzyme assays. The plant extract demonstrated inhibition of 92.6 ± 0.04% and 74.5 ± 0.04% at 0.2 mg/mL on α-glucosidase and α-amylase, respectively.…”

“…stem bark were evaluated for antidiabetic activities using α-glucosidase and α-amylase enzyme assays. Compounds lupeol 2 and β-sitosterol 16 inhibitory activities on α-glucosidase with 50% maximal inhibitory concentration (IC 50 ) values of 66.5 µM and 66.5 µM, respectively [ 72 ]. Against α-amylase, the compounds lupeol and β-sitosterol exhibited moderate activities with IC 50 values of 140.7 µM and 216.0 µM, respectively.…”

Anti-lipolytic, -amylase inhibitory and antioxidant activities of Pseuderanthemum palatiferum (Nees) Radlk. leaf ethanolic extract

“…Several phytochemicals, including -sitosterol, stigmasterol and kaempferol, were isolated from the PPE extract (Giang et al, 2003). The in vitro inhibitory activity of these phytochemicals against αamylase was demonstrated previously (Tadera et al, 2006;Nkobole et al, 2011;Takahama and Hirota, 2013). Additionally, it was reported that -sitosterol, stigmasterol and kaempferol significantly decreased the plasma glucose levels in streptozotocin-or alloxan-induced diabetic rats (de Sousa et al, 2004;Kumar et al, 2013).…”

The chemistry and bioactivity of Southern African flora I: a bioactivity versus ethnobotanical survey of alkaloid and terpenoid classes

“…146 The result demonstrated that compound 69 was one of the secondary metabolite that showed the best inhibitory activity on a-glucosidase with an IC 50 value of 66.48 mM. A bioassay-guided fractionation of an acetone extract of the stem bark of this plant by Nkobole et al led to the isolation of lupeol (69) and other known compounds.…”