Phytochemical and antioxidant analysis of Citrullus ecirrhosus seed: an in vitro and in silico evaluation towards atherosclerosis management

Abstract

Atherosclerosis is an inflammatory condition of the arteries that contributes significantly to around 84.5% of all CVD mortality. It is distinguished by lipid accumulation in coronary arteries, which results in plaque development, reduced blood flow, and oxygen availability to various body tissues. This study therefore aimed at assessing phytochemicals of Citrullus ecirrhosus seed powder from three varieties, their antioxidant potential and predicting the binding mode of HMG-CoA reductase enzyme towards phyto-compounds using in silico studies as a drive towards atherosclerosis management. Secondary metabolites were extracted from Citrullus ecirrhosus seed powder using water, methanol, ethyl acetate, chloroform and hexane, and evaluated for total phenolic content (TPC) and total flavonoid content (TFC). The polar extracts (methanol and water) had higher phenolic and flavonoid content as compared to the moderate and non-polar seed powder extracts (P < 0.05). The methanolic and water extracts also showed higher (P < 0.05) free radical scavenging capacity as compared to the other moderate and non-polar solvent extracts in the DPPH and ABTS assays. This showed that the seed powder extract was rich in polar phytochemicals as compared to the non-polar. Identification of secondary metabolites of the extract was done using GC-MS. From a range of phytochemicals identified, 19 of those had reported antioxidant activities. These are Hexadecanoic acid; methyl ester (methyl palmitate); n-Hexadecanoic acid; Phenol, 2,4-bis(1,1-dimethylethyl); γ-Tocopherol; Hydroxylamine 5-Hydroxymethylfurfural; ester; O-decyl; Vanillin 13-Octadecenoic lactoside; acid methyl Octadecanoic ester; acid; 9,10-Secocholesta-5,7,10(19)-triene-3,24,25-triol, (3β,5Z,7E); cis-Vaccenic acid; Pentanoic acid, octyl 3-Dodecene, (Z); 1-Heptatriacotano; Nonadecane; 2-Piperidinone, N-[4-bromo-n-butyl]; Heptacosane; Stigmasterol; 2-Methoxy-4-vinylphenol. The molecular interaction between HMG-CoA reductase enzyme, which is significant in cholesterol regulation, was studied against the 19 phytoconstituents from the seed powder extracts in silico. The phytoconstituents with high binding affinity within the range of that for the statins used were Vanillin lactoside, 9,10-secocholesta-5,7,10(19)-triene-3,24,25-triol, stigmasterol, gamma-Tocopherol and Phenol, 2,4-bis(1,1-dimethylethyl)-. Their binding affinities ranged from -8.2 to -6.3 kcal/mol. Vanillin lactoside showed the highest binding affinity of -8.2 kcal/mol and the interactions between the compound and the protein were predicted to be through conventional hydrogen bond, carbon hydrogen bond, Pi-Cation, Pi-Alkyl and unfavorable donor-donor interactions. This study thus showed that the Citrullus eccirhosus seeds have phytochemicals with antioxidant activity and some phytochemicals having a binding mode towards the HMG-CoA reductase enzyme in silico. However, there is also need to carry out wet lab analysis so as to confirm the ability of the seed powder in reducing the atherosclerotic lesion in atherosclerosis induced albino wistar rats.