Antibacterial, Antifungal, Antioxidant, and Docking Studies of Potential Dinaphthodiospyrols from Diospyros lotus Linn Roots.

The main aims of this investigation were the isolation of dimeric naphthoquinones, a new class of dinaphthodiospyrols (1-7), from chloroform fractions and screening them for antibacterial, antifungal, and antioxidant potential. The susceptibility of the isolated compounds, namely, dinaphthodiospyrol A (1), dinaphthodiospyrol B (2), dinaphthodiospyrol C (3), dinaphthodiospyrol D (4), dinaphthodiospyrol E (5), dinaphthodiospyrol F (6), and dinaphthodiospyrol G (7) was assessed for antibacterial potential using well diffusion methods. The isolated compounds showed excellent antibacterial activity against selected bacterial strains, including Gram-positive Bacillus subtilis, Streptococcus epidermis, and Bacillus subtilis, and Gram-negative bacteria Klebsiella pneumonia with the zones of inhibition 6 to 26 nm. The standard drug Imipenem showed a maximum inhibitory zone 30 to 35 nm. Similarly, the isolated compounds were screened for antifungal properties, which showed an excellent reduction in the growth of selected fungal strain including Candida albicans, Aspergillus flavus, Fusarium solani, Trichyton logifusus, Microsporum canis , and Candida glabrata. Among all the screened compounds, 7 exhibited good activity (30-49 mm), followed by compounds 5 and 6, (35-46 mm), while compounds 1-4 showed a moderate effect (8-28 mm) against the selected fungal strain against miconazole which showed potent effects (101-110.98 mm). The isolated compounds were also screened for 1, 1-diphenyl-2-picrylhydrazyl (DPPH) activity. In vitro-based free radical was employed using ascorbic acid as a standard antioxidant. The tested compounds (1-7) exhibited significant antioxidant activity in a concentration-dependent manner. The dinaphthodiospyrol 7 exhibited 97.32% scavenging activity, followed by dinaphthodiospyrol 6, 92.01%, and compounds 5 and 4 with 89.90 and 88.43% scavenging activity at 100 μg/mL, respectively; ascorbic acid showed 96.45% scavenging effect. Furthermore, docking analysis was performed to know the exact binding mode of the tetra-substituted derivatives of dinaphthodiospyrols to the selected target proteins. From the docking analysis, it was found that the docking results are well correlated with the experimental observations. In conclusion, the dinaphthodiospyrols exhibited excellent antibacterial, antifungal, and free radical scavenging potential.