Chemical Characterisation of Volatile Constituents of Four Nigerian Zingiber officinale Ecotypes and Their Comparative Antimicrobial Activity

Zingiber officinale (ginger) is cultivated across multiple agro-ecological zones of Nigeria, including farms in Kaduna, Nassarawa, Taraba, and Cross River States, and is used medicinally for a wide range of infectious and inflammatory conditions. Chemotypic variation in the volatile oil composition of ginger across different Nigerian growing zones may significantly affect its therapeutic potency, yet such comparative data are largely absent from the literature. This study characterises the volatile constituents of Zingiber officinale rhizomes from four Nigerian growing zones representing the North West, North Central, North East, and South South ecotypes through hydrodistillation and GC-MS analysis. Comparative antimicrobial activity of the four essential oils was evaluated against Staphylococcus aureus, Salmonella typhi, Pseudomonas aeruginosa, Aspergillus flavus, and Candida albicans by disc diffusion and MIC methods. GC-MS identified 46 to 62 volatile compounds per ecotype, with zingiberene, beta-sesquiphellandrene, curcumene, and geranial as predominant constituents. Significant quantitative variation in zingerone and shogaol concentrations was observed across ecotypes. The North East (Taraba) ecotype showed the highest zingiberene content (28.4%) and the strongest antimicrobial activity against all tested organisms. These findings demonstrate that geographical origin substantially influences Zingiber officinale chemotype and pharmacological activity, with implications for quality control and regional sourcing standards for Nigerian herbal ginger products. Keywords: Zingiber officinale, chemotype, GC-MS, essential oil, antimicrobial