Chemical composition, antioxidant capacity and antibacterial activity against some potato bacterial pathogens of fruit extracts from Phytolacca dioica and Ziziphus spina-christi grown in Egypt

Abstract

Abstract In the present study, the effects of n-hexane extracts from Phytolacca dioica L. and Ziziphus spina-christi L. fruits were evaluated against the growth of potato brown and soft rot bacterial pathogens, namely, Ralstonia solanacearum, Dickeya solani, Pectobacterium carotovorum subsp. carotovorum, Enterobacter cloacae, and Bacillus pumilus. The chemical components of the oils were analyzed using GC/MS, and the antioxidant activity was determined using 2,2-dipheny-1-picrylhydrazyl radical-scavenging (DPPH) and β-carotene-linoleic acid assays. Aromatic hydrocarbons such as 6-phenyl-dodecane and 7-phenyl-tridecane were the most abundant compounds identified in n-hexane from both fruits. Also, some volatile compounds such as α-citronellol (2.46%), and dodecane (2.27%) were found in P. dioica and m-cymene (1.95%), crypton (1.58%), and α-pinene (1.20%) found in Z. spina-christi fruit extracts. Z. spina-christi fruit extract showed antioxidant activity, with IC50 values of 5.5 ± 0.1 and 4.1 ± 0.1 μg/mL, while P. dioica fruit extract showed values of 5.2 ± 0.1 and 6.3 ± 0.1 μg/mL, as measured by DPPH and β-Carotene-linoleic acid, respectively. The minimum inhibitory concentration values for Z. spina-christi fruit extract ranged from 32 to 125 μg/mL against the studied bacteria. For P. dioica, the MIC values ranged from 32 to 64 μg/mL. The extracts from P. dioica and Z. spina-christi fruits exhibited different levels of activities against the growth of potato brown rot, soft rot and blackleg bacterial pathogens.