Antimycobacterial Metabolites from Plectranthus: Royleanone Derivatives against Mycobacterium tuberculosis Strains

Abstract

The antimycobacterial activities of eight diterpenes, 1-8, isolated previously from Plectranthus and eleven esters, 9-19, of 7alpha-acetoxy-6beta,12-dihydroxyabieta-8,12-diene-11,14-dione (5) were evaluated against the MTB strains H(37)Rv and MDR. Only diterpenoids with a quinone framework revealed anti-MTB activity. Abietane 5 and its 6,12-dibenzoyl, 12-methoxybenzoyl, 12-chlorobenzoyl, and 12-nitrobenzoyl esters, 9, 11, 12, and 13, respectively, showed potent activities against the MDR strain with MIC values between 3.12 and 0.39 microg/ml. Cytotoxic activities towards 3T3 and Vero cells were also evaluated. Compound 11, with the best selectivity index, may be a suitable lead for further chemical modifications. The complete structural elucidation of the new esters, 9-14, 16, 18, and 19, as well as the NMR data of known derivatives 15 and 17 are reported.

Antimicrobial Plant Extracts Encapsulated into Polymeric Beads for Potential Application on the Skin

“…Particularly, plants of the Plectranthus genus (Lamiaceae) have several ethnobotanical documented uses, including the treatment of various infections [1,2]. These traditional uses are well supported by the isolation of diverse antimicrobial metabolites, namely diterpenoids and polyphenols [3][4][5]. The use of herbal extracts as therapeutic agents may be an interesting area for developing countries and has aroused the interest of the population in developed countries.…”

Plants: A Source for New Antimycobacterial Drugs

“…Hedge., Lamiaceae, distributed in tropical and subtropical Africa, are traditionally used in respiratory disorder treatments. Abietane (95) and its derivatives (96-98) isolated from Plectranthus grandidentatus Gurke., Lamiaceae, were reported to have activity against MDR forms, which were better than the usual antimycobacterial agents [58]. A diterpene, kaurenoic acid (99), was isolated from P. cinereum [48].…”

Two new diterpenoids from Plectranthus species

“…In continuation of our studies on biologically active diterpenoids from Plectranthus species (Cerqueira et al, 2004;GasparMarques et al, 2004GasparMarques et al, , 2006GasparMarques et al, , 2008Rijo et al, 2002Rijo et al, , 2010, we have now investigated Plectranthus porcatus Van Jaarsv. & P. Winter (Winter and Van Jaarsveld, 2005), a species that has not hitherto been studied either chemically or pharmacologically, and Plectranthus saccatus Benth., a plant from which two beyerane diterpenoids (3 and 4, Fig.…”