Evaluation of Anti-Diabetic Activities and Profiles of Selected Eritrean Medicinal Plants

Abstract

Diabetes mellitus has become one of the largest health emergencies of the 21st century. The increase in resistance of conventional drugs, the side effects associated with the prolonged use of insulin and other hypoglycemic drugs, the unaffordable cost of buying drugs has currently brought renewed interest in plant based medicines for diabetes. Herbal drugs are cheap, readily available, safe and effective and culturally acceptable and thus WHO has recommended the investigations for alternative hypoglycemic agents from plants. The aim of the present study was to evaluate the anti-diabetic activities and profile of bioactive compounds present in the selected Eritrean medicinal plants. Based on the ethnomedicinal surveys conducted in Central and Southern Zones of Eritrea, 42 different anti-diabetic plants were identified. Preliminary phytochemical screening of the plants confirmed the presence of flavonoids, alkaloids, phenols, coumarins, steroids and others. The anti-diabetic profile of the crude methanol extracts and fractions of Aloe camperi, Meriandra dianthera and a Polyherb were initially screened using in vitro assays and elicited dose dependent inhibitory activities against α-glucosidase and α-amylase; comparable to Acarbose. Besides, the anti-diabetic activities of the extracts, using the in vivo model, showed significant decrease in the fasting blood glucose level (FBGL) by the end of the experimental day; the FBGL was significantly brought down (P < 0.001) by all the extracts at the end of the experimental day relative to the control. Moreover, the acute oral toxicity tests were estimated and the LD50 of the crude extracts was greater than 2000 mg/kg. Statistical analyses for the in vitro and in vivo experiments were performed using One-Way ANOVA followed by Dunnett’s test for multiple comparisons. The levels of trace essential elements were determined using FAAS and ICP-OES, and thus the plants contain significant levels of elements including Zn, Cr, Mn, V, Se and Mg. Identification and tentative charachterisation of bioactive phytochemicals using LC-MS, GC-MS and FT-IR displayed diverse compounds. The main bioactive compounds found in M. dianthera were flavonoids, essential oils and fatty acid methyl esters (FAMEs). Similarly, the main compounds found in A. camperi were xxi flavonoids, phenolic acids, coumarines and FAMEs. Moreover, alkaloids, paramount FAMEs, essential oils and steroids were identified in the Polyherb. Therefore, the selected anti-diabetic plants have displayed potential bioactivity and good profile of bioactive compounds and thus can be possible candidates for herbal drug development.