Exploring the phytochemical profiling and antibacterial efficacy of ripe and unripe Carissa carandas fruit extracts against gram-positive and gram-negative bacteria

Abstract

The emergence of antibiotic-resistant microorganisms has become a serious global health concern, prompting the search for effective and natural therapeutic alternatives. Carissa carandas, a plant widely used in traditional medicine, is known for its bioactive phytochemicals with potential antibacterial properties. This study aimed to investigate the phytochemical composition and evaluate the comparative antibacterial activity of ripe and unripe C. carandas fruit extracts prepared using five solvents: aqueous, methanol, ethanol, ethyl acetate, and n-hexane. Phytochemical screening was performed using standard qualitative methods, and antibacterial activity was evaluated against three Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, and Lactobacillus sporogenes) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) using the disk diffusion method. Disks were impregnated with 5, 10, 15, and 20 μL of extract solution at a concentration of 10 mg/mL. The ethyl acetate extract of unripe fruit exhibited the highest antibacterial efficacy, with maximum zones of inhibition ranging from 10 mm to 11 mm against Lactobacillus sporogenes, surpassing all other extracts. Ethyl acetate and methanol extracts of unripe fruit showed a higher diversity of secondary metabolites compared to other solvents. In contrast, aqueous extract of unripe fruit and ethanol extract of ripe fruit displayed the lowest antibacterial activity. Overall, unripe fruit extracts were more effective than ripe fruit extracts. Streptomycin was used as a reference standard. These findings validate the traditional use of C. carandas and highlight its potential as a natural source of antibacterial agents, especially the ethyl acetate extract of unripe fruit, for combating resistant bacterial strains.