Three New Abietane-Type Diterpenoids from Plectranthus africanus and Their Antibacterial Activities

Abstract

Three new abietane-type diterpenoids, plectranthroyleanones A – C (1 – 3), together with five known compounds (4 – 8) were isolated from the methanol extract of the whole plant of Plectranthus africanus using column chromatography techniques. The structures of the new compounds were elucidated using a combination of 1D and 2D NMR and HRESIMS analyses. Compound 1 exhibited weak activities with minimal inhibitory concentration values of 75 µg/mL against gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, and 150 µg/mL against two gram-negative bacteria, Pseudomonas aeruginosa and Klebsiella pneumoniae, respectively, while 2 and 3 had moderate antibacterial activity against K. pneumoniae with a minimal inhibitory concentration value of 37.5 µg/mL.

Key words

Plectranthus africanus - Lamiaceae - abietanes - plectranthroyleanone - antibacterial activity

• References

• 1 Lukhoba CW, Simmonds MSJ, Paton AJ. Plectranthus: a review of ethnobotanical uses. J Ethnopharmacol 2006; 103: 1-24
• 2 Paton AJ, Springate D, Suddee S, Otieno D, Grayer RJ, Harley MM, Willis F, Simmonds MSJ, Powell MP, Savolainen V. Phylogeny and evolution of basils and allies (Ocimeae, Labiatae) based on three plastid DNA regions. Mol Phylogenet Evol 2004; 31: 277-299
• 3 Morton JK. Cytotaxonomic studies on the West African Labiatae. J Linn Soc Bot 1962; 58: 231-283
• 4 Burkill HM. The useful plants of west tropical Africa. Vol. 3. 2nd edition. Kew: Royal Botanic Gardens; 1985: 857
• 5 Abdel-Mogib M, Albar H, Batterjee S. Chemistry of the genus Plectranthus . Molecules 2002; 7: 271-301
• 6 Sharma Y, Vasundhara M. Coleus (Plectranthus barbatus) – A multipurpose medicinal herb. Int Res J Pharm 2011; 2: 47-58
• 7 Batista O, Duarte A, Nascimento J, Simoes MF, de la Torre MC, Rodriguez B. Structure and antimicrobial activity of diterpenes from the roots of Plectranthus hereroensis . J Nat Prod 1994; 57: 858-861
• 8 Nyila MA, Leonard CM, Hussein AA, Lall N. Bioactivities of Plectranthus ecklonii constituents. Nat Prod Commun 2009; 4: 1177-1180
• 9 Stavri M, Paton A, Skelton BW, Gibbons S. Antibacterial diterpenes from Plectranthus ernstii . J Nat Prod 2009; 72: 1191-1194
• 10 Van Zyl RL, Khan F, Edwards TJ, Drewes SE. Antiplasmodial activities of some abietane diterpenes from the leaves of five Plectranthus species: research letter. S Afr J Sci 2008; 104: 62-64
• 11 Razdan TK, Kachroo V, Harkar S, Koul GL. Plectranthoic acid A & B, two new triterpenoids from Plectranthus rugosus . Tetrahedron 1982; 38: 991-992
• 12 Gaspar-Marques C, Rijo P, Simões MF, Duarte MA, Rodriguez B. Abietanes from Plectranthus grandidentatus and P. hereroensis against methicillin- and vancomycin-resistant bacteria. Phytomedicine 2006; 13: 267-271
• 13 Schmid JM, Rüedi P, Eugster CH. Diterpenoide Drüsenfarbstoffe aus Labiaten: 22 neue Coleone und Royleanone aus Plectranthus lanuginosus . Helv Chim Acta 1982; 65: 2136-2163
• 14 Batista O, Simões MF, Duarte A, Valdeira ML, de la Torre MC, Rodríguez B. An antimicrobial abietane from the root of Plectranthus hereroensis . Phytochemistry 1995; 38: 167-169
• 15 Kulkarni RR, Shurpali KD, Gawde RL, Sarkar D, Puranik VG, Joshi SP. Chemical investigation of Plectranthus mollis . J Med Aromat Plant Sci 2012; 34: 125-131
• 16 Künzle JM, Rüedi P, Eugster CH. Isolierung und Strukturaufklärung von 36 Diterpenoiden aus Trichomen von Plectranthus edulis (VATKE) T.T. AYE. Helv Chim Acta 1987; 70: 1911-1929
• 17 Alder AC, Rüedi P, Prewo R, Bieri JH, Eugster CH. Neue Diterpenoide aus Blattdrüsen einer Plectranthus sp. aus Rwanda. Helv Chim Acta 1986; 69: 1395-1417
• 18 Alder AC, Rüedi P, Eugster CH. Plectranthone A, B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae). Helv Chim Acta 1984; 67: 1003-1011
• 19 Dinga A, Braut-Boucher F, Paris M, Mercier J. Preliminary study of Labiatae originating from Africa. I. Comparative analysis of essential oils from Leocus africanus and Alvesia rosmarinifolia . Acta Hortic 1980; 96: 139-149
• 20 Tene M, Tane P, Tamokou JDD, Kuiate JR, Connolly JD. Degraded diterpenoids from the stem bark of Neoboutonia mannii . Phytochem Lett 2008; 1: 120-124
• 21 Mafodong DFL, Tsopmo A, Awouafack MD, Roland TT, Dzoyem JP, Tane P. A novel ellagic acid derivative from Desbordesia glaucescens . Nat Prod Comm 2015; 10: 1709-1710
• 22 Tene M, Tane P, Connolly JD. Triterpenoids and diarylheptanoids from Myrica arborea . Biochem Syst Ecol 2008; 36: 872-874
• 23 She G, Guo Z, Lv H, She D. New flavonoid glycosides from Elsholtzia rugulosa Hemsl. Molecules 2009; 14: 4190-4196
• 24 Lin RJ, Cheng MJ, Chen WY, Pan CY, Chang WT, Hsui YR, Hung HC, Lo WL. Phytochemical investigation and cytotoxic evaluation of components of leaves and stems of Machilus zuihoensis var. mushaensis . Chem Nat Compd 2014; 50: 978-981
• 25 Tan N, Kaloga M, Radtke OA, Kiderlen AF, Öksüz S, Ulubelen A, Kolodziej H. Abietane diterpenoids and triterpenoic acids from Salvia cilicica and their antileishmanial activities. Phytochemistry 2002; 61: 881-884
• 26 Edwards OE, Feniak G, Los M. Diterpenoid quinones of Inula royleana DC. Can J Chem 1962; 40: 1540-1546
• 27 Hensch M, Rüedi P, Eugster CH. Horminon, Taxochinon und weitere Royleanone aus 2 abessinischen Plectranthus-Spezies (Labiatae). Helv Chim Acta 1975; 58: 1921-1934
• 28 Yoshizaki F, Rüedi P, Eugster CH. Diterpenoide Drüsenfarbstoffe aus Labiaten: 11 Coleone und Royleanone aus Coleus carnosus HASSK. Helv Chim Acta 1979; 62: 2754-2762
• 29 Moujir L, Gutierreznavarro AM, Sanandres L, Luis JG. Structure-antimicrobial activity relationships of abietane diterpenes from Salvia species. Phytochemistry 1993; 34: 1493-1495
• 30 Eloff JN. A sensitive and quick microplate method to determine the minimal inhibitory concentration of plant extracts for bacteria. Planta Med 1998; 64: 711-713
• 31 Awouafack MD, Ito T, Tane P, Kodama T, Tanaka M, Asakawa Y, Morita H. A new cycloartane-type triterpene and a new eicosanoic acid ester from fruits of Paullinia pinnata L. Phytochem Lett 2016; 15: 220-224