Microwave-assisted extract of rhodomyrtone from <i>rhodomyrtus tomentosa</i> leaf: Anti-inflammatory, antibacterial, antioxidant, and safety assessment of topical rhodomyrtone formulation
Julalak C. Ontong, Sudarshan Singh, Ozioma Forstinus Nwabor, Sarunyou Chusri, Wijittra Kaewnam, Kanyanatt Kanokwiroon, Abdi Wira Septama, Pharkphoom Panichayupakaranant, Supayang Piyawan Voravuthikunchai
Abstract
Series of works on the biological properties of rhodomyrtone, a major active component of Rhodomyrtus tomentosa leaf has been reported. In this study, rhodomyrtone-rich microwave-assisted extract from R. tomentosa leaf (RT-MAE) before formulation was profiled for phytochemical composition using gas chromatography-mass spectrometry (GC-MS) and targeted for anti-inflammatory activity with topical application. The formulation was assessed for bioactivity, biocompatibility, and safety on human volunteers. The GC-MS spectra indicated a rich content of phytosterols, sesquiterpenes, and acylphloroglucinols. At concentrations 50–600 ng/mL, RT-MAE before formulation treated macrophages showed >86% cell viability. Nitric oxide production significantly decreased by 19.26–88.36% following the treatment with 50–600 ng/mL RT-MAE before formulation (p < 0.001). Moreover, a significant (p < 0.01) concentration-dependent downregulation of lipopolysaccharide-induced IL-6, IL-1β, iNOS, and COX-2 mRNA was observed in RT-MAE before formulation treated macrophages. The extract demonstrated minimum inhibitory (MIC) and minimum bactericidal concentration (MBC) at 0.25–4 and 1–16 μg/mL, respectively. The antioxidant activity of RT-MAE before formulation indicated IC50 of 0.16 and 0.06 ug/mL for DPPH and ABTS assays, respectively. Ex-vivo diffusion of rhodomyrtone from formulation showed steady-state flux 64.935 ng/cm2 h, with >80% viability on HaCaT cells. Safety assessment of formulation containing RT-MAE after formulation was conducted on healthy volunteers. Hematological and biochemical analysis showed no significant difference between test and baseline (p < 0.05). The results suggested that the formulation can be effectively employed as a topical inflammatory agent.