Free radical scavenging capacity, antibacterial activity and essential oil composition of turmeric (Curcuma domestica) varieties grown in Ethiopia

Turmeric is a known spice indispensable for food preparation and is reported to possess different chemical properties and biological activities. The objective of this study was to determine the effects of variety and type of extracts on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) reducing capacity, antibacterial activity, and chemical composition of essential oil from turmeric varieties cultivated in Ethiopia. The results from the statistical analysis revealed that the highest total curcuminoids content (6.81% m/m), essential oil (6.37% v/m), methanol extract (13.42% v/m) were obtained from Dame variety. On the other hand, the lowest curcuminoids (5.12% m/m), methanol extract (10.58% v/m) and essential oil (3.92% v/m) contents were obtained from HT3/2002 variety. Dame variety also had the highest total polyphenol content (97.55 mg GAE/g) and radical scavenging capacity (46.58 16 μg/mL) with the lowest IC(50) value (23.05 μg/mL). Among the tested microorganisms with turmeric extracts, growth inhibition was observed against S. aureus. The results also indicated that three compounds, namely α-Turmerone (32.41 and 35.16%), ar-Turmerone (25.20 and 25.47%), and Curlone (17.98 and 18.19%) dominated 75% of the essential oil component in Dame and Bonga 51/71 varieties, respectively. In summary, the results of this study revealed that extracts from Dame variety have strong biological potential with desired antioxidant and antibacterial activities.