Fusarium oxysporum is one of the most harmful soil-borne pathogens that cause root rot, damping-off, and wilt disease in many plant species. Management of Fusarium oxysporum diseases is often by using many harmful and expensive chemical fungicides which have many harmful effects on the environment and human health. The current study was conducted to identify the chemical constituents of black cumin seeds’ methanolic extract and investigate the ability of the major constituents to inhibit the Fusarium oxysporum trypsin-like serine protease, which play an important role in F. oxysporun pathogenicity. The HPLC-MS analysis of black cumin seeds’ methanolic extract revealed the presence of seven major compounds: amentoflavone, Procyanidin C2, Quercetin3-O-sophoroside-7-O-rhamnoside, 5,7-Dihydroxy-3,4-dimethoxyflavone, Borapetoside A, tetrahydroxy-urs-12-en-28-O-[b-D-glucopyranosyl (1-2)-b-D-glucopyranosyl] ester, and kudzusapongenol A-hexA-pen. The results of molecular docking between these compounds and the active site of Fusarium oxysporium trypsin showed that only four compounds were able to bind to the active site of F. oxysporum trypsin. Amentoflavone, 5,7-Dihydroxy-3,4-dimethoxyflavone, and Quercetin3-O-sophoroside-7-O-rhamnoside have the highest binding energy, −6.4, −6.5, and −6.5 Kcal/mol, respectively. In addition, the results clarify that 5,7-Dihydroxy-3,4-dimethoxyflavone was the only compound to form a hydrogen bond with Asp189 (the residue responsible for substrate specificity). The results of the study strongly indicate that flavonoids of black cumin seeds’ methanolic extract could be used as effective inhibitors for the F. oxysporum trypsin-like serine protease.

The present study was conducted to evaluate the ability of different extracts of cinnamon and black cumin seeds to inhibit the growth of the phytopathogenic fungus Rhizoctonia solani and its extracellular cell wall degrading enzymes. The results clearly demonstrated that concentrations of 300 or 450 ppm of methylene chloride or hexane extracts of cinnamon completely inhibited the growth of R. solani after 72hours of incubation at 25±1°C in vitro. Methylene chloride or hexane extracts of black cumin seeds at 4000 ppm inhibited the growth of R. solani by 37% and 39% after72 hours of incubation respectively. Moreover, black cumin seeds hexane extract at 2000 ppm inhibited 55% and 38% of the activity of pectin lyase (PL) and polygalacturonase (PG) respectively. In addition, the methanolic extract of black cumin seeds at 2000 ppm exhibited a significant reduction of exo-protease activity (74.8%). GC- MS analysis results showed that linoleic acid is the main component of the fixed oil fraction of black cumin seeds hexane extract while (E)-cinnamaldehyde is the main component in both hexane and methylene chloride extracts of cinnamon. HPLC-MS analysis of black cumin seeds methanolic extract showed that amentoflavone, was the main component.