Chemical Composition and Antibacterial Activity of Essential Oil Extracted from Citrus sinensis L., Citrus limon L. and Zingiber officinale Roscoe

Oloche JJ^{1,3 *}  Gabriel AD^2,3 Ubwa ST^2,3 Amokaha RA.⁴

¹Department of Pharmacology & Therapeutics College of Health Sciences, Benue State University Makurdi, Nigeria

²Department of Chemistry, Benue State University Makurdi, Nigeria

³Centre for Food Technology and Research, Benue State University Makurdi, Nigeria

⁴Department of Medical Biochemistry, College of Health Sciences, Benue State University Makurdi, Nigeria.

*Correspondence: Oloche JJ

Email: jerry_oloche@yahoo.com

Abstract
Postharvest loss is a serious problem in Nigeria and a major drawback towards food security. Hence, discovery of potential agents capable of minimizing postharvest loss is urgently needed. This research is directed at investigating the in vivo antimicrobial activity of essential oils against bacterial pathogens isolated from Ipomoea batatas Lam, Citrus sinensis and Citrus limon peels and Zingiber officinale essential oils were extracted using hydro-distillation and their chemical constituents determined by gas chromatography mass spectrometry (GC-MS). Morphological and biochemical methods were employed for bacterial identification. A total of 22 terpenes were identified with Citrus sinensis comprising 13 monoterpenes, 8 sesquiterpenes and 1 diterpene. Citrus limon had 31 terpenes 15 of which are monoterpenes, 15 sesquiterpenes and 1 diterpene while a total of 30 terpenes were identified with Zingiber officinale comprising of 12 monoterpenes and 18 sesquiterpenes. Three of the four isolated bacteria identified from Hannah sweet potato were pathogenic: Erwinia carotovora, Bacillus licheniformis and Pseudomonas fluorescens. Pseudomonas fluorescens was more sensitive to the essential oils at (p≤0.05). Citrus sinensis (64.29%, 9.0±0.00 mm) was three fold more active than Citrus limon (21.43%, 3.0±0.00 mm), while Zingiber officinale (53.57%, 7.5±0.71 mm) was two and a half fold more active than Citrus limon. Results obtained in this study showed that essential oils extracted from Citrus sinensis and Zingiber officinale exhibited substantial antimicrobial activity against bacterial induced sweet potato rot. Therefore, essential oils extracted from Zingiber officinale and Citrus sinensis could be used to control postharvest bacteria induced rots in injured sweet potatoes.

Keywords: Postharvest losses, Pathogens, Bacteria isolates, Antibacterial activity, Sweet potato rot