Antifungal and antioxidant potential of Ocimum species against Ascochyta rabiei (Pass) Lab

Cicer arietinum L. is a vital source of nutrients that suffers substantial annual losses due to Ascochyta blight, caused by the plant pathogen Ascochyta rabiei. This study aimed to investigate the antifungal potential of Ocimum tenuiflorum L. and O. basilicum L. shoots (leaves and stems) against A. rabiei (Pass) Lab. In vitro bioassays were conducted using methanolic extracts from leaves and stems at six different concentrations: 1%, 1.5%, 2%, 2.5%, 3%, and 3.5%. A total of eight compounds were identified through gas chromatography-mass spectrometry (GC-MS) analysis. The highest inhibition of A. rabiei growth was achieved with a 3.5% methanolic leaf extract of O. basilicum. Methanolic extracts from O. tenuiflorum shoots also reduced fungal growth by 6.18-73%. Additionally, the n-hexane fraction derived from O. basilicum inhibited fungal growth by 71-76% and was subsequently analyzed using GC-MS. This analysis identified eight compounds: (1) cyclopentane, methyl-, (2) cyclohexane, (3) 2,2-dimethylbutane, (4) 2,3-dimethylbutane, pentane, (5) 2,3-dimethyl-, (6) 2-bromoacetonitrile, (7) alpha-cadinol, and (8) phenylpropanolamine. The antioxidant activity of O. tenuiflorum and O. basilicum shoots was also assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The highest antioxidant activity, 98.58%, was recorded at a 3.5% methanolic stem extract concentration of O. tenuiflorum. The antioxidant activity potential was highest for O. tenuiflorum at 0.729mg/mL, followed by O. basilicum at 0.411mg/mL.