Plectranthus zeylanicus: A Rich Source of Secondary Metabolites with Antimicrobial, Disinfectant and Anti-Inflammatory Activities

Abstract

Plectranthus zeylanicus Benth is used in Sri Lankan folk medicine as a remedy for inflammatory conditions and microbial infections. Our previous investigations revealed potent 5-lipoxygenase (5-LO) inhibitory activity in lipophilic extracts of this plant, supporting its anti-inflammatory potential. In-depth studies on the antimicrobial activity have not been conducted and the bioactive ingredients remained elusive. As a continuation of our previous work, the present investigation was undertaken to evaluate the antimicrobial activity of different extracts of P. zeylanicus and to isolate and characterize bioactive secondary metabolites. Different organic extracts of this plant were analyzed for their antibacterial activity, and the most active extract, i.e., dichloromethane extract, was subjected to bioactivity-guided fractionation, which led to the isolation of 7α-acetoxy-6β-hydroxyroyleanone. This compound displayed strong antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimum inhibitory concentration of 62.5 µg/mL, and its disinfectant capacity was comparable to the potency of a commercial disinfectant. Moreover, 7α-acetoxy-6β-hydroxyroyleanone inhibits 5-LO with IC50 values of 1.3 and 5.1 µg/mL in cell-free and cell-based assays, respectively. These findings rationalize the ethnopharmacological use of P. zeylanicus as antimicrobial and anti-inflammatory remedy.

Improving Foodborne Pathogen Control Using Green Nanosized Emulsions of Plectranthus hadiensis Phytochemicals

“…Sripathi, Jayagopal, and Ravi [47] reported an MIC value of 320 µg/mL for S. aureus and E. coli in extracts obtained by hydrodistillation. In contrast, the methanolic extracts obtained by Napagoda et al [48] showed an MIC of 500 µg/mL for S. aureus and 1000 µg/mL for Salmonella typhi. In addition, Ntungwe et al [38] reported an MIC and MBC value of 15.6 µg/mL and 250 µg/mL, respectively, for S. aureus in the ultrasound-assisted extract and Schultz et al [42] obtained an MIC of 104 µg/mL for S. aureus and an MIC of >500 µg/mL for E. coli and Listeria innocua.…”

“…However, Kotagiri, Shaik, and Kolluru [8], as well as Sripathi and Ravi [46], reported that in addition to having antimicrobial activity against Gram-positive bacteria, PHT extracts also showed activity against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. According to Sripathi, Jayagopal, and Ravi [47], the antimicrobial activity of P. hadiensis can be attributed to the presence of monoterpenes and sesquiterpenes, mainly L-fenchone, β-farnesene, copaene, and α-caryophyllene, while Dominguez-Martín et al [10] and Napagoda et al [48] ascribe the antimicrobial activity mainly to the diterpenes 7α-acetoxy-6βhydroxyroyleanone, 7 β-acetoxy-6β-hydroxyroyleanone, and 6β,7β-dihydroxyroyleanone.…”

Anticancer Effects of Abietane Diterpene 7α-Acetoxy-6β-hydroxyroyleanone from Plectranthus grandidentatus and Its Semi-Synthetic Analogs: An In Silico Computational Approach

“…Specifically, this compound suppresses 5-LO product formation in cell-free assays with an IC 50 of 1.3 µg/mL and in human neutrophils with an IC 50 of 5.1 µg/mL. Therefore, the inhibition of 5-LO and leukotriene production appears to be an anti-inflammatory mode of action of 7α-acetoxy-6β-hydroxyroyleanone [38]. Roy also displays immunosuppressive activity by inhibiting lymphocyte proliferation.…”

“…The current research has focused on the compound 7α-acetoxy-6β-hydroxyroyleanone (Roy) isolated from the P. grandidentatus; it belongs to the broader class of abietanes that encompasses a diverse array of plant-derived diterpenoid compounds demonstrating promising biological effects, including antibacterial, anti-inflammatory, and immunomodulatory properties, as well as cytotoxic activities in numerous cancer cell lines [35][36][37][38][39][40].…”

Exploring the Anticancer Potential of Semisynthetic Derivatives of 7α-Acetoxy-6β-hydroxyroyleanone from Plectranthus sp.: An In Silico Approach

“…Roy displays strong antibacterial activity against methicillin-resistant Staphylococcus aureus strains with a minimum inhibitory concentration (MIC) of 62.5 µg/mL [39]. Due to its high antibacterial potency and low cytotoxicity, Roy is a promising alternative to current antibiotics for treating infections caused by resistant bacteria.…”