Vol. 7, Issue 2, Part G (2025)

The escalating crisis of antimicrobial resistance (AMR) necessitates the urgent exploration of novel, naturally derived antibacterial agents. Plant secondary metabolites represent a promising reservoir for such compounds. This study investigates the phytochemical composition and antimicrobial potential of Vitis vinifera (grape) skin, a significant agri-food by-product. An ethanolic extract was prepared from authenticated grape skins, yielding 22% w/w. Preliminary phytochemical screening confirmed a rich repertoire of bioactive constituents, including abundant flavonoids, anthocyanins, tannins, and phenolic compounds.

A comprehensive metabolic profile was elucidated using Gas Chromatography-Mass Spectrometry (GC-MS), which revealed a complex mixture of high-value lipophilic compounds. The extract was characterized by a high concentration of fatty acid esters (e.g., Ethyl Palmitate), phytosterols (e.g., γ-Sitosterol), and tocopherols (Vitamin E), underpinning its potent antioxidant and emollient properties. The antimicrobial efficacy was evaluated against clinically relevant Gram-positive (Staphylococcus aureus MTCC 7443) and Gram-negative (Escherichia coli MTCC 2665) pathogens via the standardized Kirby-Bauer disk diffusion assay.

The results demonstrated selective and significant antibacterial activity. The extract (100 mg/mL) produced a distinct zone of inhibition (7mm) against S. aureus, surpassing the activity of the standard antibiotic amoxicillin (13mm) under the tested conditions. Conversely, no inhibitory activity was observed against E. coli. This differential efficacy is attributed to the structural disparity in bacterial cell envelopes; the impermeable outer membrane of Gram-negative E. coli likely acts as a barrier to the extract's bioactive molecules, whereas the more permeable peptidoglycan layer of Gram-positive S. aureus is susceptible to disruption.

In conclusion, Vitis vinifera skin extract is established as a rich source of antioxidants and emollients with selective antibacterial activity. While its application as a broad-spectrum antimicrobial is limited, its pronounced effect against S. aureus and its rich phytochemical profile validate its potential as a valuable, sustainable ingredient for developing topical formulations in the cosmetic and nutraceutical industries, and warrant further investigation into its active principles for combating Gram-positive infections.