Phytocompounds Profiling and Assessment of the Antioxidant and Anti-diabetic Potentials of Methanol Extracts of Garcinia kola (Heckel)

Abstract

Background: Nigeria is endowed with many medicinal plants which are yet to be exploited for their medicinal values. The purpose of this study is to investigate the chemical constituents using GC-MS and assess the antioxidant and anti-diabetic properties of Garcina kola, Aims: The aim of this study was to described the phytochemical constituents, antioxidant and anti-diabetic activities of methanol extracts of the leaf, stem and root of Garcinia kola (Heckel). Study Design: The study was designed to evaluate the phytochemical constituents, antioxidants and anti-diabetic potentials of methanol extracts of the leaves, stem bark and root bark of Garcina kola (Heckel) grown in Nigeria. Place and Duration of Study: Fresh leaves, stem barks and root barks of G. kola were collected from a location in Abeokuta, Ogun state Nigeria. Methodology: Extract were obtained from the air-dried leaves, stem barks and root barks of Garcina kola by maceration in methanol for 48 h. Afterwards the various extracts were concentrated in vacuo. Phytochemical screenings were analysed by conventional methods while the various phytocompounds were determined by suing gas chromatography-mass spectrometry technique. The antioxidant activity of the various extracts was tested by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The antidiabetic potential was assessed by evaluating the inhibitory effect of the extracts on the activities of α-amylase and α-glucosidase enzymes. Results: The main compounds identified by GC/MS in the leaf extract were hexadecanoic acid (15.28%), 2-butenedioic acid (14.23%), and 6-hydroxy-4,4,7a-trimethyl-5,6,7,7-tetrahydrobenzofuran-2(4H)-one (12.69%). The stem bark consists mainly of Phenol (20.88%), 1-propanone (18.06%) and 9-octadecenoic acid (11.21%), while ethyl 2-(5-methyl-5-tetrahydrofuran-2-yl) propan-2-yl carbonate (13.77%), phenol (13.34%), decanoic acid (8.79%) and hexadecanoic acid (7.74%) were the main compounds of the root extract. At a concentration of 100 µg/mL, the leaves, stem barks and root barks exhibited 80 ±0.01%, 82 ±0.00% and 79 ±0.01% DPPH radical scavenging activity. All the studied Garcina extracts displayed IC₅₀ value of 3.7 µgmL-1, when compared with Ascorbic acid which exhibited IC50 value of 2.5 µgmL-1 against DPPH. The inhibitory potency of G. kola extracts against α-amylase activity were concentration dependent. All extracts showed higher potency at 100 µg/mL, with inhibitory percentages of 93 ±0.00 (leaves), 91 ±0.01 (stem bark) and 89 ±0.01 (root barks). At a concentration of 100 µg/mL, all the extracts displayed good inhibition of α-glucosidase enzyme activity at percentages of 75 ±0.00, 74 ±0.01 and 72 ±0.01, respectively. The extracts displayed almost equal and similar activity against the inhibition of α-Amylase enzymatic activity, with IC50 values between 5.50 µgmL-1 - 5.80 µgmL-1. While Acarbose exhibited IC50 value of 1.70 µgmL-1 towards α-Glucosidase enzyme, the extracts showed values ranging from 4.80- 5.00 µgmL-1 α-Glucosidase enzyme. Conclusion: G. kola contains phytochemicals with promising antidiabetic and antioxidant activities which can serve as a source of future lead drugs for combating oxidative stress related diseases.