Two antihyperglycaemic compounds from Globimetula braunii (Engl.) Van Tiegh (Loranthaceae)

Abstract

Large numbers of medicinal plants are constantly being screened for possible pharmacological values, especially for chronic diseases such as diabetes, with the view of discovering new compounds that may serve as templates for synthesis of more active/less toxic drugs. Therefore, the antihyperglycaemic activity of the leaf of Globimetula braunii with antidiabetic ethnomedical usage in Nigeria was investigated is this study to justify this folkloric claim. The median lethal dose, LD50 of the ethanol leaf extract of G. braunii was determined using Lorke's method and its antihyperglycaemic effect at 100, 200 and 400 mg/kg was evaluated using glucose-induced hyperglycaemic rats while glibenclamide (5 mg/kg) and 1 % Tween 80 in normal saline served as positive and negative controls, respectively. Anti-hyperglycaemic activity-directed purification of the extract of the plant in glucose-loaded rats, led to the isolation and characterisation of phyllanthone and methyl 2, 6-dihydroxy-4-methoxybenzoate from the dichloromethane partitioned fraction. The findings showed that the LD50 of the ethanol leaf extract of G. braunii was greater than 5,000 mg/kg while its 100 mg/kg was the most active dose with comparable activity (p>0.05) to the standard drug, glibenclamide. The dichloromethane and aqueous partitioned fractions of the extract were the most promising fractions. Chromatographic separations of the dichloromethane fraction yielded phyllanthone, and methyl 2, 6dihydroxy-4-methoxybenzoate that elicited comparable activity to glibenclamide (5 mg/kg) at 10 and 20 mg/kg at all time-points. The study justified the antidiabetic folkloric use of G. braunii leaf and confirmed phyllanthone and methyl 2,6-dihydroxy-4-methoxybenzoate as two of its antihyperglycaemic constituents.

Ursane-Type Triterpenes, Phenolics and Phenolic Derivatives from Globimetula braunii Leaf

“…While the C=O attachment at the C-3 position was based on the HMBC experiment. Upon consideration of the spectra of 1-3 and in comparison with spectra data on similar compounds reported in the literature, they were identified as 13,27-cycloursane (1), 13,27-cycloursan-3-one previously identified as phyllanthone (2) and hexadecahydro-8-hydroxy-9-(2-hydroxy-6-methylheptyl)-1,2,6a,6b,9,12a-hexamethyl-6bHcyclopropa[q]picen-10(11H,12bH,15H)-one (3), named globraunone [15][16][17].…”

“…(Family Loranthaceae) is a hemi-parasitic and epiphytic plant that derives water and mineral nutrients from its hosts by means of a specialized root system called "haustorium" [1]. It is commonly called "African Mistletoe" and locally called "Afomo Onisano" in Southwest Nigeria [2]. The plant is mostly found on dicot trees, such as Piliostigma thonningii, Leucena leucocephala and Theobroma cacao, where it becomes bushy and woody, growing up to 5 ft in diameter until the host tree withers [3].…”