Phytochemical analysis and antibacterial activity of Citrullus lanatus var. citroides (Citron watermelon) fruit and the effect of temperature on the biological activity of the rind

The use of indigenous plants for food, water and medicinal purposes dates back to decades of years. In southern Africa the fruit flesh and rind of Citrullus lanatus var. citroides are cooked as porridge with maize meal and served to sick people by traditional healers. The seeds are dried, roasted and eaten as nuts or ground into flour to make bread. The aim of this study was to determine the biological activities of the seed and flesh of Citrullus lanatus var. citroides fruit and evaluate the effect of temperature on rind bioactivity. The rind was exposed to various temperatures. Total phenolics, tannins, flavonoids, nutritional content and antioxidant activity were estimated using spectrometric methods. Antibacterial activity was determined using microbroth dilution and bioautography. Total polyphenolic contents were greatest in the seeds, followed by the flesh and rind respectively. Potassium was the most abundant element present in the flesh, seeds and untreated rind control. The flesh had higher antioxidant activity than the rind and seeds. Pseudomonas aeruginosa was the most susceptible pathogen for both the seeds and flesh where minimum inhibitory concentrations between 0.02-0.31 mg/mL were determined. High temperatures led to a significant loss in rind bioactivity. Lower temperatures must be considered when preparing C. lanatus var. citroides products to preserve the potential therapeutic properties which supplement its nutritional content. (c) 2022 SAAB. Published by Elsevier B.V. All rights reserved.

Automated summary

This study aims to investigate the biological activities of seed and flesh of Citrullus lanatus var. citroides fruit and evaluate the effect of temperature on rind bioactivity. The results showed that the seeds had the highest total polyphenolic content, the flesh had higher antioxidant activity, and high temperatures led to a loss in rind bioactivity.