Investigating the Antioxidant, Pro-Inflammatory Enzyme Inhibitory, Neuroprotective, and Antineuroinflammatory Bioactives of Osbeckia octandra Using In Vitro and In Silico Approaches: A Pilot Study.

Osbeckia octandra (Melastomataceae) is an endemic Sri Lankan edible plant traditionally used for liver health. Oxidative stress, pro-inflammatory enzyme-mediated hepatic inflammation, and neuroinflammation are interconnected conditions that exacerbate liver diseases. The study investigates the antioxidant, pro-inflammatory enzyme inhibitory, neuroprotective, and antineuroinflammatory potential of the bioactives from O. octandra. The leaves were sequentially extracted with petroleum ether, ethyl acetate, and ethanol using a cold extraction technique. Antioxidant activity was evaluated using DPPH free radical scavenging and oxygen radical absorbance capacity (ORAC) assays. Pro-inflammatory enzyme inhibition was assessed using lipoxygenase (LOX), xanthine oxidase, hyaluronidase, and nitric oxide production inhibition assays. Bioassay-guided fractionation was conducted using chromatography techniques, and the compounds were characterized using spectroscopic techniques. In silico investigations computationally validated the promising experimental findings. The ethyl acetate extract showed the highest LOX inhibition (IC50: 36.21 ± 1.09 μg/mL), the highest DPPH free radical scavenging activity (IC50: 42.29 ± 1.29 μg/mL), and the highest ORAC (470.33 ± 3.16 mg TE/g). The LOX inhibition-guided fractionation of the ethyl acetate and petroleum ether extracts led to the isolation of the compounds casuarinin (1) and lupeol (2), respectively. Casuarinin (1) showed strong, dose-dependent anti-LOX (IC50: 33.94 ± 0.59 μg/mL) and antioxidant activities. In silico investigation predicted that casuarinin (1) forms multiple hydrogen bonds at the LOX active site despite kinetically limited active site access. Casuarinin (1) exhibited dose-dependent (13.3-213.3 μM) antineuroinflammatory properties (>50%) in mouse microglia cells. It also demonstrated significant neuroprotective effects on H2O2-induced apoptotic SH-SY5Y neuroblastoma cells, with a notable increase in cell viability at 10.7 μM (73.74 ± 2.04%) and 106.7 μM (99.07 ± 1.43%). The bioactives from O. octandra exhibited significant antioxidant, LOX enzyme inhibitory, antineuroinflammatory, and neuroprotective properties, substantiating its therapeutic potential, positioning it as a promising candidate for phytotherapeutic applications.