In Vitro Antimicrobial Activity of Isopimarane-Type Diterpenoids

Abstract

The antimicrobial evaluation of twelve natural and hemisynthetic isopimarane diterpenes are reported. The compounds were evaluated against a panel of Gram-positive bacteria, including two methicillin-resistant Staphylococcus aureus (MRSA) strains and one vancomycin-resistant Enterococcus (VRE) strain. Only natural compounds 7,15-isopimaradien-19-ol (1) and 19-acetoxy-7,15-isopimaradien-3β-ol (6) showed promising results. Isopimarane (1) was the most active, showing MIC values between 6.76 µM against S. aureus (ATCC 43866) and 216.62 µM against E. faecalis (FFHB 427483) and E. flavescens (ATCC 49996). Compound (6) showed moderated activity against all tested microorganisms (MIC between value 22.54 and 45.07 µM). These compounds were found to be active against the methicillin-sensitive strains of S. aureus (CIP 106760 and FFHB 29593), showing MIC values of 13.55 (1) and 22.54 (6) µM. Both compounds were also active against vancomycin-resistant E. faecalis (ATCC 51299) (MIC values of 54.14 and 45.07 µM, respectively). In addition, the cytotoxicity of nine compounds 7,15-isopimaradien-3β,19-diol (2); mixture: 15-isopimarene-8β-isobutyryloxy-19-ol and 15-isopimarene-8β-butyryloxy-19-ol (3); 3β-acetoxy-7,15-isopimaradiene-19-ol (5); 19-acetoxy-7,15-isopimaradiene-3β-ol (6); 3β,19-diacetoxy-7,15-isopimaradiene (8); 15-isopimarene-8β,19-diol (9); 19-O-β-d-glucopyranoside-7,15-isopimaradiene (10); lagascatriol-16-O-β-d-glucopyranoside (11) and lagascatriol-16-O-α-d-mannopyranoside (12) was evaluated in the human breast cancer cell line MDA-MB-231. Isopimarane (2) was the only compound showing some cytotoxicity. The IC50 value of compound (2) was 15 µM, suggesting a mild antiproliferative activity against these breast cancer cells.

Pimarane Diterpenoids from Aerial Parts of Lycopus lucidus and Their Antimicrobial Activity

“…In a previous study, 3and 19-hydroxyl groups of isopimarane compounds were acetylated to investigate the role of substituents on antimicrobial activity. e results indicated that if acetylation occurs in the 3-hydroxyl position or both 19-and 3-hydroxyl groups, the antibacterial activity gets reduced significantly [27]. Hence, our study also revealed a similar result.…”

Preliminary Biological Activity Screening of Plectranthus spp. Extracts for the Search of Anticancer Lead Molecules

“…Phytochemical studies on some species of Plectranthus revealed the presence of a large number of diterpenes and triterpenes [ 10 , 11 ]. Isolated terpenes from Plectranthus species are reported to possess antibacterial [ 12 , 13 , 14 ], antitumoral [ 15 , 16 , 17 , 18 ], antifungal [ 12 , 19 ], insecticidal [ 20 ], and antiplasmodial [ 20 ] activities. Moreover, our group has been focused on the phytochemical study of Plectranthus species and we have reported abietane diterpenoids with diverse bioactivity [ 16 , 17 , 21 , 22 , 23 , 24 , 25 ].…”

Antimicrobial Diterpenes: Recent Development From Natural Sources

“…The diterpene 63 also exhibited potent antibacterial activity with MIC values ranging between 22.54 and 45.07 µM against all tested strains of S. aureus and all species of Enterococcus. The other diterpenes did not show any antimicrobial potency ( Isca et al, 2020 ).…”