Bioactive Constituents of the Stem Bark of Mitrephora glabra

Abstract

Bioactivity-guided fractionation of the stem bark of Mitrephora glabra yielded nine compounds, comprising three ent-kaurenoids (1-3), five polyacetylenic acids/esters (4-8), and one aporphine alkaloid, liriodenine (9). The structures of the six new compounds (1-3, 5, 7, and 8) were determined by spectroscopic data interpretation. All compounds were evaluated for their inhibitory activities against a panel of cancer cell lines and a battery of microorganisms.Over the last two decades, plants of the Annonaceae have been investigated rather extensively, largely for the presence of cytotoxic and/or insecticidal acetogenins. 1 Of these natural productbased investigations, however, the genus Mitrephora is relatively under-explored, probably because Annonaceous acetogenins have not been discovered therein, at least to date. There are nearly 50 described species of Mitrephora, and although a few species are relatively widespread in its native range, which extends from mainland China in the north to India in the west to Australia in the southeast, most of these shrubs and small to large trees have very narrow to localized distributions. [2][3][4] Representatives of such ecological niches may yield secondary metabolites of unique structures; yet, to the best of our knowledge, only five species of Mitrephora have been investigated for bioactive secondary metabolites, specifically, M. celebica ,5,6 M. maingayi ,7-9 M. thorelii, 10,11 M. tomentosa ,12 and M. zippeliana In an ongoing study of potential anticancer agents from the plant kingdom, 14,15 an investigation of the constituents of the stem bark of Mitrephora glabra Scheff. (Annonaceae), collected in Indonesia, has been conducted. In an earlier communication, we reported from this plant three new ent-trachylobane diterpenoids, mitrephorenones AC, of which one was shown to possess an unusual oxetane ring, making it the first hexacyclic representative of this compound class. 16 A more comprehensive investigation of this species, with the aim of isolating more potent cytotoxic constituents led to the isolation and elucidation of six additional new compounds (1-3, 5, 7, and 8) and three known substances (4, 6, 9). These can be subdivided into three entkaurane diterpenoids (1-3) and five polyacetylenic acids/esters (4-8). The known alkaloid, liriodenine (9), for which the structural data were in good agreement with those in the literature, 17,18 was isolated as well. This alkaloid was reported recently from M. maingayi 9 and may be common to species in the Mitrephora genus; it has been found in at least two other genera of the Annonaceae as well. 17 Along with testing in cytotoxicity assays, all compounds were evaluated for antimicrobial activity, largely due to the literature precedence for antimicrobial constituents from this genus. 5,6 Results and DiscussionCompound 1 exhibited a molecular formula of C 20 H 30 O 2 , as deduced from HREIMS and 1D NMR data, suggesting an index of hydrogen deficiency of six. An examination of the literature quickly led to the known ...

Anticancer Activities of Polyynes from the Root Bark of Oplopanax horridus and Their Acetylated Derivatives

“…To date, pharmacological investigations have revealed that polyynes from natural sources show antibacterial, anti-fungal, antiinflammatory, nerotoxic and anticancer activities [6][7][8][9]. Polyynes were regarded to be responsible for many bioactivities of Oplopanax horridus, which has long history of medicinal use and as a dietary supplement.…”

ent-Kaurane diterpenoids from the plant Wedelia trilobata

“…It was confirmed by, the HMBC correlations from H-11 ( H 5.00, dd, J = 3.7, 3.1 Hz) to C-8 ( C 45.9, C), C-10 ( C 38.1, C), and C-13 ( C 38.8, CH), as shown in Figure 1. The α-orientation of the carboxylic acid group at C-4 was inferred from the 13 C NMR chemical shift of the methyl group at C-4 by comparing those of related entkaurane diterpenoids, in which the methyl group with β-orientation resulted in resonance of approximately δ C 29, as opposed to resonance of approximately δ C 16 when the methyl group was in the α-orientation. 7,13,14 Accordingly, the structure of compound 2 was elucidated as ent-17-hydroxykaura-9 (11) , resembled those of (3R,4R,6S)-3,6-dihydroxymenth-1-ene.…”

Chemical constituents of Anacolosa pervilleana and their antiviral activities

“…octadeca-9,11,13-triynoic acid [10] (2), (13E)-octadec-13-en-9,11-diynoic acid [11] (3), (13E)-octadec-13-en-11-ynoic acid [9] (4), lupenone [12] (5), β-amyrone [13] (6), and (S)-sambunigrin [14] (7) was elucidated through comparison with literature data. The acetylenic products are usually unstable, undergoing photolytic or pH-dependent oxidation leading to their decomposition [15].…”