Isolation and characterization of a fatty acid from the seed extracts of citrullus lanatus (water melon)

Abstract

A sample of powdered watermelon seeds sample was macerated with ethanol for two weeks using a maceration method. The mixture was stirred using magnetic stirrer, for 24 hours, in order to extract the powders. It was then decanted, filtered and concentrated on a rotavapor (R110) at 40 ºC in order to obtain the crude ethanol extract (F001). The crude ethanol extract was partitioned into aqueous methanol, chloroform, ethyl acetate and acetone in order to obtain F002, F003, F004 and F005 fractions respectively. The methanol fraction indicated strong activity in the antimicrobial test compared to other fractions. Based on these results, the methanol fraction was subjected to activity-guided chromatographic purification targeting the compound responsible for the observed activity. The methanol fraction (10 g) of the extracted seeds of Citrullus lanatus was chromatographed on a silica gel column, using different eluents. This afforded 117 fractions which were combined based on their thin layer chromatography (TLC) pattern. The pooled fraction (-62 – 67-) was further chromatographed in order to obtain the fatty acid. The structure of the compound was characterized – using,- Proton nuclear magnetic resonance (¹H NMR), Carbon-13 nuclear magnetic resonance (¹³C NMR), Distortionless enhancement bypolarization transfer (DEPT), Fourier transform infrared spectroscopy (FTIR) spectroscopic techniques and Mass spectrometry (MS) analysis in order to propose the structure of the compound as a straight chain aliphatic dicarboxylic acid (3-methylnonadec-4,6-diene1,19-dioic acid).