New Cytotoxic Tigliane Diterpenoids from Croton caudatus

Combining DNA and HPTLC profiles to differentiate a pain relief herb, Mallotus repandus, from plants sharing the same common name, “Kho-Khlan”

The pain relief formula “Ya Pa Som Kho-Khlan (YPSKK)” or “ยาผสมโคคลาน” in Thai is officially recorded in the Natural List of Essential Medicines (NLEM) of Thailand. The main component is Mallotus repandus (Willd.) Müll. Arg.; however, Anamirta cocculus (L.) Wight & Arn and Croton caudatus Gleiseler share the same common name: “Kho-Khlan”. Confused usage of A. cocculus or C. caudatus can have effects via toxicity or unsuccessful treatment. This study aimed to combine a high-performance thin-layer chromatography (HPTLC) technique and DNA barcoding coupled with high-resolution melting (Bar-HRM) to differentiate M. repandus from the other two species. The M. repandus extract exhibited a distinct HPTLC profile that could be used to differentiate it from the others. DNA barcodes of the rbcL, matK, ITS and psbA-trnH intergenic spacer regions of all the plants were established to assist HPTLC analysis. The rbcL region was selected for Bar-HRM analysis. PCR amplification was performed to obtain 102 bp amplicons encompassing nine polymorphic nucleotides. The amplicons were subjected to HRM analysis to obtain melting curve profiles. The melting temperatures (T_m) of authentic A. cocculus (A), C. caudatus (C) and M. repandus (M) were separated at 82.03±0.09°C, 80.93±0.04°C and 80.05±0.07°C, respectively. The protocol was applied to test crude drugs (CD1-6). The HPTLC profiles of CD2-6 showed distinct bands of M. repandus, while CD1 showed unclear band results. The Bar-HRM method was applied to assist the HPTLC and indicated that CD1 was C. caudatus. While ambiguous melting curves from the laboratory-made formulae were obtained, HPTLC analysis helped reveal distinct patterns for the identification of the plant species. The combination of HPTLC and Bar-HRM analysis could be a tool for confirming the identities of plant species sharing the same name, especially for those whose sources are multiple and difficult to identify by either chemical or DNA techniques.

Gastrointestinal discomfort and hypotension in a patient with Reutealis trisperma seeds intoxication: A case report

RATIONALE

Reutealis trisperma is a plant belonging to the Euphorbiaceae family and Reutealis genus and is often mistaken for a plant of the genus Aleurites. Accidental ingestion of R trisperma seeds is relatively rare in Taiwan than that of Vernicia fordii. Mostly, the clinical course of R trisperma seed poisoning is similar to that of V fordii poisoning. Recent studies have shown that the median lethal dose 50 of R trisperma seeds in mice is approximately 4954 mg/kg. R trisperma seed extract has a significant effect on the autonomic nervous system by causing ptosis and disrupting breathing, and affects the central nervous system by reducing motor activity.

PATIENT CONCERNS

A 51-year-old man with underlying gout and hepatitis B picked several seeds of R trisperma, which he misidentified at chestnuts, at an elementary school. He prepared soup by boiling 3 to 4 seeds and consumed it. He experienced abdominal pain, vomiting, and watery diarrhea with hypotension.

DIAGNOSIS

R trisperma seeds intoxication.

INTERVENTIONS

The patient was given a soft diet, input and output were recorded, and intravenous fluid supplements were administered.

OUTCOMES

The patient was discharged after 3 days of hospitalization, once a relatively stable condition was achieved.

LESSONS

Human poisoning by accidental consumption of R trisperma seeds is relatively rare in Taiwan. It may cause gastrointestinal symptoms and even hypotension. Patients can recover within 2 to 3 days of receiving proper treatment and intravenous fluid infusion.

Two highly oxygenated nor-clerodane diterpenoids from Croton caudatus

Two highly oxygenated nor-clerodane diterpenoids, crocleropenes A and B (1 and 2), together with four known compounds (3-6) were isolated from the leaves and twigs of Croton caudatus. Their structures were elucidated by combination of extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. 1 and 2 represent the first examples of nor-clerodane-3,5(10)-diene diterpenoids. Compounds 1 and 2 exhibited weak cytotoxicity in vitro against MCF-7 cancer cells with IC₅₀ values of 35.8 and 40.2 μM, respectively. [Formula: see text].

Anti-HIV tigliane diterpenoids from Reutealis trisperma

Bioassay-guided fractionation of the n-butanol extract from the branches and leaves of Reutealis trisperma resulted in the isolation of six undescribed (crotignoids L ~ Q) together with two known (12-deoxyphorbol-13-hexadecanoate and 12-deoxyphorbol-13-myristate) tigliane diterpenoids. Their structures, especially the absolute configurations, were determined from extensive spectroscopic studies, including 2D NMR spectra, CD data analysis and electronic circular dichroism (ECD) calculations. All isolates were tested for anti-HIV activity against HL4-3 virus in MT4 cells. Except for crotignoid Q, the remaining seven tigliane diterpenoids exhibited potent anti-HIV activity with IC₅₀ values ranging from 0.0023 to 4.03 μM.

Cytotoxic 8,9-seco-ent-kaurane diterpenoids from Croton kongensis

Chemical study on the ethanolic extract generated from the aerial parts of Croton kongensis led to the isolation of three new 8,9-seco-ent-kaurane diterpenoids, kongeniods A‒C (1‒3), together with seven known analogs (4-10). The structures of these compounds were assigned by spectroscopic data analysis. The vitro cytotoxic tests showed that compounds 1-3 exhibited strong activities against HL-60 cell lines with IC₅₀ values of 0.47, 0.58, and 1.27 μM, respectively.

Six new diterpenoids from Croton laevigatus

Six new ent-labdane-type diterpeniods (1‒6), along with one known compound, were identified from the twigs and leaves of Croton laevigatus. Their structures were elucidated on the basis of extensive spectroscopic interpretation. Compounds 2 and 7 showed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with IC₅₀ values of 4.11 and 8.33 μg/ml, respectively.

Chemical Constituents from Croton Species and Their Biological Activities

The genus Croton belongs to the Euphorbiaceae family, which comprises approximately 1300 species. Many Croton species have been used as folk medicines. This review focuses on the chemical constituents from Croton species and their relevant biological activities, covering the period from 2006 to 2018. A total of 399 new compounds, including 339 diterpenoids, were reported. Diterpenoids are characteristic components of the Croton species. These isolated compounds exhibited a broad spectrum of bioactivities, including cytotoxic, anti-inflammatory, antifungal, acetylcholinesterase inhibitory, and neurite outgrowth-promoting properties. The present review provides a significant clue for further research of the chemical constituents from the Croton species as potential medicines.

Survey of natural products reported by Asian research groups in 2016

The new natural products reported in peer-reviewed articles in 2016 in journals with good reputations were reviewed and analyzed. The advances that Asian research groups made in the field of natural products chemistry in 2016 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on structural classification.

Cytotoxic Indole Alkaloid 3α-Acetonyltabersonine Induces Glioblastoma Apoptosis via Inhibition of DNA Damage Repair

Cytotoxic indole alkaloids from Melodinus suaveolens, which belongs to the toxic plant family Apocynaceae, demonstrated impressive antitumor activities in many tumor types, but less application in glioblastoma, which is the lethal brain tumor. In the present study, we reported the anti-glioblastoma activity of an indole alkaloid, 3α-acetonyltabersonine, which was isolated from Melodinus suaveolens. 3α-acetonyltabersonine was cytotoxic to glioblastoma cell lines (U87 and T98G) and stem cells at low concentrations. We verified 3α-acetonyltabersonine could suppress tumor cell proliferation and cause apoptosis in glioblastoma stem cells (GSCs). Moreover, detailed investigation of transcriptome study and Western blotting analysis indicated the mitogen activated protein kinase (MAPK) pathway was activated by phosphorylation upon 3α-acetonyltabersonine treatment. Additionally, we found 3α-acetonyltabersonine inhibited DNA damage repair procedures, the accumulated DNA damage stimulated activation of MAPK pathway and, finally, induced apoptosis. Further evidence was consistently obtained from vivo experiments on glioblastoma mouse model: treatment of 3α-acetonyltabersonine could exert pro-apoptotic function and prolong the life span of tumor-bearing mice. These results in vitro and in vivo suggested that 3α-acetonyltabersonine could be a potential candidate antitumor agent.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, abietanes, pimaranes, kauranes, cembranes and their cyclization products. The literature from January to December, 2016 is reviewed.