Diterpenoids from Leaves of Cultivated Plectranthus ornatus

Abstract

Two new diterpenoid derivatives 7α,12β,17-triacetoxy-6β,19-dihydroxy-13β,16-spirocicloabiet-8-ene-11,14-dione (1) and 6β-acetoxy-3β,7α,12α-trihydroxy-13β,16-spirocicloabiet-8-ene-11,14-dione (2) along with 11 (3–13) miscellaneous compounds were isolated from the leaves of Plectranthus ornatus Codd. Their structures were elucidated by spectroscopic analysis and gauge independent atomic orbitals 13C NMR calculations. The isolated compounds were screened for their effects on intestinal motility using guinea-pig ileum and duodenum and by their cytotoxicity against 4 human cancer cell lines (HCT-116, SF-295, PC-3, and HL-60). Compounds 6 and 9 were moderately cytotoxic against HL-60, whereas 6 and 13 were more active on SF-295 and HCT-116.

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 ].…”

Diterpenes Isolated from Three Different Plectranthus Sensu Lato Species and Their Antiproliferative Activities against Gynecological and Glioblastoma Cancer Cells

“…The NOE correlations, H-12/ H-16b, H-15/H-16b, H-16a/H-17a, and H-16a/H-17b, implied a cis relationship between the 15-acetoxymethyl group and the carbonyl at C-14, as originally suggested. 11 However, a correlation H-12/H 3 -20 and the absence of the previously reported correlation H-12/H-15 11 placed H-12 in the β-pseudoaxial position (Figures S8, Supporting Informa-tion). In addition, the original assignment for CH 2 -1 and CH 2 -3 11 was interchanged (Tables 1 and 2) based on the HMBC cross-peaks, H-1a/C-9, H-1a/C-20, H-1b/C-9, H-1b/C-20, H-3b/C-18, and H-3b/C-19 (Figures S7, Supporting Information).…”

Abietane Diterpenes of the Genus Plectranthus sensu lato

“…It was previously assumed that all spirocoleons are (12 R )-isomers with an α-oriented hydroxyl [ 70 ]. Although most spirocoleons belong to the (12 R )-isomers, the existence of 7β-acetyl-12-desacetoxycyclobutatusine ( 106 ) and ornatin F ( 136 ), isolated in 2007 and 2020, respectively, showed that (12 S )-isomers with a β-orientation of the hydroxyl group exist in nature [ 77 , 78 ].…”

“…The air-dried leaves and stems of C. lanuginosus were extracted successively with hexane and diethyl ether [ 60 ]. The air-dried leaves of C. comosus were macerated with hexane followed by ethanol [ 77 ]. Extraction of plant material at room temperature under sonication has also been described in several studies, e.g., the aerial parts of C. forsteri ‘Marginatus’ [ 38 ] and C. madagascariensis [ 54 ] were extracted with methanol in an ultrasonic bath.…”

“…Mesquita et al, 2021, isolated abietane diterpenes from C. comosus using different chromatographic methods: column chromatography (using silica gel and Sephadex LH-20 as stationary phase), semi-preparative HPLC (using C18 column and normal phase column), and flash chromatography (using silica gel) [ 77 ].…”