Microwave-assisted extract of rhodomyrtone from rhodomyrtus tomentosa leaf: Anti-inflammatory, antibacterial, antioxidant, and safety assessment of topical rhodomyrtone formulation

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.

KEYWORDS:

• Antibacterial
• Anti-inflammatory
• Anti-oxidant
• Biomedicine
• Rhodomyrtone
• Rhodomyrtus tomentosa

Acknowledgments

The research was supported by the National Research Council of Thailand Project (Grant Number N41A640071) and Postdoctoral Fellowship was supported by Prince of Songkla University and the Ministry of Higher Education, Science, Research and Innovation, Thailand, under the Reinventing University Project (Grant Number REV64050).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualization, J.C.O., S.P.V., S.S., S.C., W.A., P.P.; data curation, J.C.O., S.S., O.F.N., W.A., W.M., J.K., S.C., W.K.; formal analysis, J.C.O., S.P.V., S.S., S.C.; funding acquisition, S.P.V., J.C.O.; Investigation, J.C.O., S.S.; methodology, J.C.O., S.S., S.C., W.A., W.M., W.K., K.K., Supervision, S.P.V., W.A.; writing – original draft preparation, J.C.O., S.S., O.F.N., W.K.; writing – review and editing, J.C.O., S.S., O.F.N., A.W.S., S.P.V. All authors have read and agreed to the published version of the manuscript.

Statement of novelty

Hereby we confirm that the manuscript entitled “Microwave-assisted extract of rhodomyrtone from Rhodomyrtus tomentosa leaf: Anti-inflammatory, antibacterial, antioxidant, and safety assessment of topical rhodomyrtone formulation” is novel and else were not published.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/01496395.2023.2169162.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The work was supported by the National Research Council of Thailand [N41A640071]; Ministry of Higher Education, Science, Research and Innovation, Thailand [REV64050]