Quantification of Anti‐Addictive Alkaloids Ibogaine and Voacangine in In Vivo‐ and In Vitro‐Grown Plants of Two Mexican Tabernaemontana Species

Tabernaemontana alba and Tabernaemontana arborea are Apocynaceae species used in Mexican traditional medicine for which little phytochemical information exists. In this study, preliminary gas chromatography/mass spectrometry analyses of different organs obtained from wild plants of both species identified a total of 10 monoterpenoid indole alkaloids (MIAs) and one simple indole alkaloid, nine of which were reported for the first time in these species. Furthermore, callus cultures were established from T. alba leaf explants and regeneration of whole plants was accomplished via somatic embryogenesis. The anti‐addictive MIAs ibogaine and voacangine were then quantified by gas chromatography with flame ionization detection in wild plants of both species, as well as greenhouse‐grown plants, in vitro‐grown plantlets and embryogenic callus of T. alba. Ibogaine and voacangine were present in most samples taken from the whole plants of both species, with stem and root barks showing the highest concentrations. No alkaloids were detected in callus samples. It was concluded that T. alba and T. arborea are potentially viable sources of ibogaine and voacangine, and that these MIAs can be produced through somatic embryogenesis and whole plant regeneration of T. alba. Approaches to increase MIA yields in whole plants and to achieve alkaloid production directly in cell cultures are discussed.     

Cytotoxic monoterpenoid indole alkaloids from the leaves and twigs of Tabernaemontana bovina

Phytochemical investigation of the leaves and twigs of Tabernaemontana bovina led to the isolation of 10 monoterpenoid indole alkaloids, including two new taberbovinines A (1) and B (2) along with eight known analogs: mehranine (3), 14α,15β-dihydroxy-N-methylaspidospermidine (4), (16S*)− 15-epi-E-isositsirikine (5), (16R*)− 15-epi-E-isositsirikine (6), 16 R*-19,20-E-isositsirikine acetate (7), hecubine (8), voafinidine (9), and voacangarine (10). Taberbovinine B (2) represents the first case of an unusual ring C/D cleavage among the natural Corynanthe-type alkaloids. Compounds 2 and 8 exhibited weak cytotoxicity against five human cancer cell lines, including SK-LU-1, HepG2, MCF-7, SK-Mel-2, and LNCaP, with IC₅₀ values ranging from 42.9 to 66.3 μM, whereas compounds 4 − 6 and 9 were cytotoxic toward MCF-7, SK-LU-1 and LNCaP cells, with IC₅₀ values in a range of 51.6–93.3 μM.     

Chemical constituents from Lonicera japonica flower buds and their anti-hepatoma and anti-HBV activities

Three new naturally occurring monoterpenoids, japopenoid A (1), japopenoid B (23) japopenoid C (24), and one new caffeoylquinic acid derivative (28), together with thirty-one known compounds (2–22, 25–27, 29–35), were isolated and identified from the flower buds of Lonicera japonica Thunb. Their structures were determined by extensive 1D and 2D NMR spectroscopic methods, high-resolution mass spectrometry, and the absolute configurations of 1, 23, 24 were determined by comparison of their electronic circular dichroism (ECD) spectrum with literature and theoretical calculation. Structurally, compound 1 is a monoterpenoid featured with an unusual tricyclic skeleton. All compounds (1–35) were evaluated for their cytotoxicities against human liver cancer cell lines (HepG 2 and SMMC-7721). Compound 12 exhibited the most potent activity with IC₅₀ values of 26.54 ± 1.95 and 8.72 ± 1.57 μg/ml against HepG 2 and SMMC-7721, and the IC₅₀ values of compound 13 were 26.54 ± 1.95 and 12.35 ± 1.43 μg/ml, respectively. Western blot results further proved that compound 13 induces hepatoma cell apoptosis via the intrinsic apoptosis pathway. In addition, most terpenoids showed inhibitory activity against HBsAg and HBeAg secretion, and HBV DNA replication. In particular, 25 μg/mlof compound 11 inhibits HBsAg and HBeAg secretion, and HBV DNA replication by 39.39 ± 5.25, 15.64 ± 1.25, and 16.13 ± 4.10% compared to the control (p < 0.05). These results indicated that L. japonica flower buds could be served as functional food for anti-hepatoma and anti-HBV activities.     

Identification of a low vindoline accumulating cultivar of Catharanthus roseus (L.) G. Don by alkaloid and enzymatic profiling

The Madagascar periwinkle [Catharanthus roseus (L.) G. Don] is a commercially important horticultural flower species and is the only source of the monoterpenoid indole alkaloids (MIAs), vinblastine and vincristine, key pharmaceutical compounds used to combat a number of different cancers. The present study uses high performance liquid chromatography for metabolic profiling of the MIAs extracted from seedlings and young leaves of 50 different flowering cultivars of C. roseus to show that, except for a single low vindoline cultivar (Vinca Mediterranean DP Orchid), they accumulate similar levels of MIAs. Further enzymatic studies with extracts from young leaves and from developing seedlings show that the low vindoline cultivar has a 10-fold lower tabersonine-16-hydroxylase activity than those of C. roseus cv. Little Delicata. It is concluded that rapid metabolic and more selective enzymatic profiling of Catharanthus mutants could be useful for the identification of a range of altered MIA biosynthesis lines.     

Monoterpenoid glycoside derivatives from Melaleuca alternifolia

The phytochemical investigation of leaves of Melaleuca alternifolia (Maiden & Betche) Cheel led to the isolation of a new monoterpenoid glycoside derivative melaleuoside (1), together with four known monoterpenoid glycoside derivatives (2–5). Structure elucidation of these compounds was performed based on NMR spectral data and MS. Compounds 2–5 were isolated from the genus of Melaleuca for the first time. Furthermore, we also discussed the chemotaxonomic significance of the isolates in this thesis.     

Chemical constituents from the calyces of Physalis alkekengi var. franchetii

One new monoterpenoid glycoside (1), together with seven known compounds, including two alkaloids (2–3), three phenylpropanoids (4–6), and two nucleosides (7–8) were isolated from the calyces of Physalis alkekengi var. franchetii. Their structures were elucidated by a combination of detailed spectroscopic analyses, chemical methods, and comparison with reported data. These eight compounds were isolated for the first time from the genus Physalis. The chemotaxonomic significance of these compounds was summarized.     

Terpenoids with cytotoxic activity from the branches and leaves of Pyrus pashia

Twenty terpenoids, including a new triterpenoid (1) and a new monoterpenoid (20), were isolated from the branches and leaves of Pyrus pashia. The structures of two new compounds were determined to be 2α, 3β, 27-trihydroxyolean-12-en-28-oic acid (1) and (4α)-3-(5,5-dimethyltetrahydrofuranyl)-1-buten-3-ol 3-O-β-d-glucopyranoside (20) on the basis of spectroscopic analysis (IR, HRESIMS, 1D and 2D NMR) and chemical method. Some of the isolated compounds were evaluated for their cytotoxic activity against a panel of human cancer cell lines by MTT assay, using cisplatin as a positive control. Compound 14 exhibited cytotoxic activities against A549 (IC₅₀ = 19.18 ± 4.26 μM), Hela (IC₅₀ = 12.56 ± 3.89 μM), SGC7901 (IC₅₀ = 10.48 ± 1.95 μM) and NHI-1975 (IC₅₀ = 7.38 ± 2.31 μM) cell lines as well as compound 12 displayed cytotoxic activities against A549 (IC₅₀ = 14.71 ± 1.47 μM) and Hela (IC₅₀ = 12.22 ± 1.88 μM) cell lines.     

Synthesis and Biological Evaluation with Plant Cells of New Fosmidomycin Analogues Containing a Benzoxazolone or Oxazolopyridinone Ring

Fosmidomycin, 3-(N-formyl-N-hydroxyamido) propylphosphonic acid sodium salt, is an efficient inhibitor of 1-deoxy-D-xylulose-5-phosphate (DOXP) reductoisomerase, the second enzyme of the 2C-methyl-D-erythritol-4-phosphate (MEP) pathway notably present in Plasmodium species. We have synthesized a new series of analogues of fosmidomycin, containing a benzoxazolone, benzoxazolethione or oxazolopyridinone ring. As the MEP pathway is involved in the biosynthesis of all isoprenoids, accumulation of ajmalicine in Catharanthus roseus cells was chosen as a marker of monoterpenoid indole alkaloid (MIA) production. None of the twelve studied phosphonic esters 3 and phosphonic acids 4 affected periwinkle cell growth, but some of them (3c, 3e, 3g and 3h) showed a significant inhibition of ajmalicine accumulation: 45–85% at 125?μM. Surprisingly, this effect disappeared by conversion of 3c and 3g into the corresponding acids 4c and 4g, respectively.