Tabernaemontana L. (Apocynaceae): A review of its taxonomy, phytochemistry, ethnobotany and pharmacology☆

Catharanthus roseus (L.) G. Don is a herbal plant traditionally used by local populations in India, South Africa, China and Malaysia to treat diabetes. The present study reports the in vitro antioxidant and antidiabetic activities of the major alkaloids isolated from Catharanthus roseus (L.) G. Don leaves extract. Four alkaloids—vindoline I, vindolidine II, vindolicine III and vindolinine IV—were isolated and identified from the dichloromethane extract (DE) of this plant's leaves. DE and compounds I-III were not cytotoxic towards pancreatic β-TC6 cells at the highest dosage tested (25.0 µg/mL). All four alkaloids induced relatively high glucose uptake in pancreatic β-TC6 or myoblast C2C12 cells, with III showing the highest activity. In addition, compounds II-IV demonstrated good protein tyrosine phosphatase-1B (PTP-1B) inhibition activity, implying their therapeutic potential against type 2 diabetes. III showed the highest antioxidant

https://www.mdpi.com/1420-3049/18/8/9770/pdf

Antidiabetic and antioxidant properties of alkaloids from Catharanthus roseus (L.) G. Don.

Titanacycles derived from reductive coupling of nitriles, alkynes, acetaldehyde, and carbon dioxide with bis(pentamethylcyclopentadienyl)(ethylene)titanium(II)

Hydroxylation of tabersonine at the C-16 position, catalyzed by tabersonine 16-hydroxylase (T16H), initiates the synthesis of vindoline that constitutes the main alkaloid accumulated in leaves of Catharanthus roseus. Over the last decade, this reaction has been associated with CYP71D12 cloned from undifferentiated C. roseus cells. In this study, we isolated a second cytochrome P450 (CYP71D351) displaying T16H activity. Biochemical characterization demonstrated that CYP71D12 and CYP71D351 both exhibit high affinity for tabersonine and narrow substrate specificity, making of T16H, to our knowledge, the first alkaloid biosynthetic enzyme displaying two isoforms encoded by distinct genes characterized to date in C. roseus. However, both genes dramatically diverge in transcript distribution in planta. While CYP71D12 (T16H1) expression is restricted to flowers and undifferentiated cells, the CYP71D351 (T16H2) expression profile is similar to the other vindoline biosynthetic genes reaching a maximum in young leaves. Moreover, transcript localization by carborundum abrasion and RNA in situ hybridization demonstrated that CYP71D351 messenger RNAs are specifically located to leaf epidermis, which also hosts the next step of vindoline biosynthesis. Comparison of high- and low-vindoline-accumulating C. roseus cultivars also highlights the direct correlation between CYP71D351 transcript and vindoline levels. In addition, CYP71D351 down-regulation mediated by virus-induced gene silencing reduces vindoline accumulation in leaves and redirects the biosynthetic flux toward the production of unmodified alkaloids at the C-16 position. All these data demonstrate that tabersonine 16-hydroxylation is orchestrated in an organ-dependent manner by two genes including CYP71D351, which encodes the specific T16H isoform acting in the foliar vindoline biosynthesis.

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A Pair of Tabersonine 16-Hydroxylases Initiates the Synthesis of Vindoline in an Organ-Dependent Manner in Catharanthus roseus

Seven new indole alkaloids of the Aspidosperma type, jerantinines A−G (1−7), were isolated from a leaf extract of the Malayan Tabernaemontana corymbosa. The structures were established using NMR and MS analysis. Five of the alkaloids isolated and two derivatives (1−5, 8, 9) displayed pronounced in vitro cytotoxicity against human KB cells (IC50 < 1 μg/mL).

Kunesch N

Papers

Carbon-13 nuclear magnetic resonance spectroscopy of naturally occurring substances. XIX. Aspidosperma alkaloids.