Comprehensive Chemical Characterisation of Volatile Compounds in Ogiri (Fermented Parkia biglobosa Seeds) from Niger State and Correlation with Antimicrobial Activity

Ogiri is a traditional condiment produced by fermentation of locust bean seeds (Parkia biglobosa) and is widely used across North Central Nigeria, including Niger State, as a flavouring agent and in traditional wound healing. The volatile chemistry of ogiri produced under indigenous fermentation conditions in Niger State and its relationship to antimicrobial properties have not been systematically characterised. This study profiled the volatile chemical composition of six ogiri samples from Minna, Bida, and Kontagora communities and correlated this with in vitro antimicrobial activity. Volatile compounds were extracted by simultaneous distillation-extraction and analysed by GC-MS with NIST library matching. Antimicrobial activity was assessed against S. aureus, E. coli, P. aeruginosa, and C. albicans by agar well diffusion and minimum inhibitory concentration determination. A total of 58 volatile compounds were tentatively identified, dominated by pyrazines, aldehydes, and short-chain fatty acids including isobutyric acid and isovaleric acid. Minna samples contained significantly higher pyrazine concentrations attributable to higher fermentation temperature. All samples showed antimicrobial activity, with Minna ogiri demonstrating the broadest spectrum and lowest MICs. Principal component analysis revealed a strong positive correlation between pyrazine content and antimicrobial activity score. These findings establish a chemical basis for the traditional antimicrobial use of ogiri and identify pyrazine compounds as key contributors to its bioactive properties. Keywords: ogiri, Parkia biglobosa, GC-MS, volatile compounds, antimicrobial activity.