Research topic: Endless exploration for natural products: dedicated to the 80th birthday of Prof. SUN Han-Dong

Prof. Puno Pema-Tenzin, Kunming Institute of Botany, Chinese Academy of Sciences. Prof. Puno Pema-Tenzin is mainly engaged in the research of Natural Products Chemistry, and majorly focused on the basic and applied basic research for the secondary metabolites and their bioactivities from two economically and medicinally important phytogroup (Schisandraceae and  Isodon ) and their endophytic fungi.

Title: Endless exploration for natural products: dedicated to the 80th birthday of Prof. SUN Han-Dong

[Abstract] Natural Products always exhibit more intellectual bioactivities and atom economy, and it's also an important source of innovative drugs. At present, the research on natural products has attracted great attention not only from natural product chemists, but also from pharmacologists, chemical biologists, and organic synthetic chemists and others. Natural products have started to play an increasingly important role in the modern multidisciplinary collaborative model. Prof. SUN Han-Dong, Academician of Chinese Academy of Sciences from Kunming Institute of Botany, has made outstanding contributions to our field, natural product chemistry, in China. He was born in November 1939 in Baoshan City, Yunnan Province, China. Over the past five decades since his graduation from Yunnan University in 1962, he has been engaged in basic and applied research on the exploration of plant-derived medicines and natural perfumes, phytochemistry and drug development. Prof. SUN and his group have systematically studied more than 260 species in China, including those of the genus Isodon, the Taxaceae, Schisandraceae, Umbelliferae, and Lauraceae family, and lichens. Among more than 3400 compounds isolated and identified from them, about 1400 new ones including many novel skeletons or new types were discovered. More than 20 new ones were found to be promising in further development and application, and a class Ⅴ new drugs for the treatment of acute cerebral infarction has been completed the clinic trials. The research results mentioned above, especially the diverse and bioactive chemical constituents from the genus Isodon and Schisandraceae family, not only promote the development of terpene chemistry, but also enriched the content of natural products in the world, and has been become one of the most successful examples of systematic research in our field.

Cite this article as: KONG Ling-Yi. Endless exploration for natural products: dedicated to the 80 th birthday of Prof. SUN Han-Dong [J]. Chin J Nat Med, 2019, 17(12): 881-882.

Title: Difficulties in research of Chinese medicine polysaccharides
[Abstract] Polysaccharides from Chinese medicines are attracting increasing attention to their wide range of valuable biological activities. As these polysaccharides are mostly from edible materials, their safety can be greatly ensured. Therefore, the Chinese medicine polysaccharides have been the focus of research and development of new drugs and health products. However, there are rarely successful cases. Here, based on the authors' own research experience, the difficulties and challenges in chemical analysis and mechanism study of Chinese medicine polysaccharides are discussed, in the hope of eliciting more innovative ideas and solutions.
Cite this article as:  LI Li-Feng, WONG Tin-Long, HAN Quan-Bin. Difficulties in research of Chinese medicine polysaccha-rides [J]. Chin J Nat Med, 2019, 17(12): 883-886.

Title: Chemical constituents and biological activities of lycophytes and ferns
[Abstract] Lycophytes and ferns are unique and charismatic members of many terrestrial ecosystems and occupy the pivotal position in land plant origin and evolution. The Chinese lycophytes and ferns flora, with approximately 2000 species, contributes a substantial component to the global lycophytes and ferns diversity, with estimates of 12 000 species. Among them, about 433 species are medicinally recorded and researches based on their phytochemical properties are important topics in natural medicines. This paper reviewed the research history and current status of chemical constituents and biological activities of lycophytes and ferns, which had highlighted the research progress of our group.

Cite this article as: ZHU Qin-Feng, ZHAO Qin-Shi. Chemical constituents and biological activities of lycophytes and ferns [J]. Chin J Nat Med, 2019, 17(12): 887-891.

Title: Leucosceptroid B from glandular trichomes of Leucosceptrum canum reduces fat accumulation in Caenorhabditis elegans through suppressing unsaturated fatty acid biosynthesis
[Abstract] Obesity that is highly associated with numerous metabolic diseases has become a global health issue nowdays. Plant sesterterpenoids are an important group of natural products with great potential; thus, their bioactivities deserve extensive exploration. RNA-seq analysis indicated that leucosceptroid B, a sesterterpenoid previously discovered from the glandular trichomes of Leucosceptrum canum, significantly regulated the expression of 10 genes involved in lipid metabolism in Caenorhabditis elegans. Furthermore, leucosceptroid B was found to reduce fat storage, and downregulate the expression of two stearoyl-CoA desaturase (SCD) genes fat-6 and fat-7, and a fatty acid elongase gene elo-2 in wild-type C. elegans. In addition, leucosceptroid B significantly decreased fat accumulation in both fat-6 and fat-7 mutant worms but did not affect the fat storage of fat-6; fat-7 double mutant. These findings indicated that leucosceptroid B reduced fat storage depending on the downregulated expression of fat-6, fat-7 and elo-2 and thereby inhibiting the biosynthesis of the corresponding unsaturated fatty acid. These findings provide new insights into the development and utilization of plant sesterterpenoids as potential antilipemic agents.

Title: Four new sesquiterpene derivatives from Dendrobium findlayanum
[Abstract]Three new sesquiterpene glycosides with alloaromadendrane and ylangene-derived type aglycones, named dendrofindlayanosides A-C ( 1-3 ), one new cyclopacamphane type sesquiterpene named dendrofindlayanobilin A ( 4 ), together with five known compounds have been isolated from stems of Dendrobium findlayanum. Their structures were determined on the basis of spectroscopic and chemical methods.

Title: A pair of new tirucallane triterpenoid epimers from the stems of Picrasma quassioides
[Abstract] A pair of new tirucallane triterpenoid epimers, picraquassins M and N ( 1 and 2 ), were isolated from the stems of Picrasma quassioides (D. Don) Benn. Their structures were determined based on comprehensive spectroscopic and X-ray crystallographic analyses. In addition, their AChE inhibitory activity, cytotoxicity against five human tumour cell lines (SW480, MCF-7, HepG2, Hela, and PANC-1), and antimicrobial activity against two bacteria (Staphylococcus. aureus 209P and Escherichia coli ATCC0111) and two fungi (Candida albicans FIM709 and Aspergillus niger R330) were evaluated.

Title: Highly oxygenous trichilin-type limonoids from Trichilia sinensis
[Abstract] Six new trichilin-type limonoids ( 1-6 ) with C-19/29 lactol or acetal bridge and a new ring intact limonoid ( 7 ) were isolated from the desiccative ripe fruits of Trichilia sinensis. Their structures were determined by extensive spectroscopic methods including 1H NMR, 13C NMR, HSQC, HMBC, ROESY experiments as well as HRESI-MS data. All isolated compounds were evaluated for toxicities against human pulmonary carcinoma A549 and Hela cell lines by sulforhodamine B (SRB) method. Compound 7 showed weak inhibitory activity in Hela cell line at 40 μmol·L-1.

Title: Four new corynanthe-type alkaloids from the roots of Alstonia scholaris
[Abstract] Four new corynanthe-type alkaloids, meloslines C-F ( 1-4 ), together with four known ones ( 5-8 ) were isolated from the roots of Alstonia scholaris. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Compounds 1 and 2 exhibited potent vasorelaxant activity on endothelium-intact renal arteries precontracted with KCl.

Title: Chemical constituents from Vernonia bockiana
[Abstract] A new sesquiterpenoid and two pregnane steroids, named vernobockolide C ( 1 ) and vernobockones A and B ( 2 and 3 ), respevtively, along with a known sesquiterpenoid, 7, 10-epoxy-11-hydroxy-bisabol-2-en-15-al, were isolated from the aerial part of Vernonia bockiana. Their structures were elucidated on the basis of extensive spectroscopic data analysis, especially 2D NMR (HSQC, HMBC, and ROESY). This study further expands the chemical space of this underexplored species.

Title: Two folate-derived analogues from an aqueous decoction of Uncaria rhynchophylla
[Abstract]Two new folate-derived analogues, named uncarophyllofolic acids A ( 1 ) and B ( 2 ), respectively, were isolated from the Uncaria rhynchophylla hook bearing stem (Gouteng in Chinese). The distinct stereochemical structures of 1 and 2 were determined by spectroscopic data analysis in combination with acidic hydrolysis and Marfey's derivatization, along with comparison of their specific rotation and Cotton effect (CE) data with those of the biogenetically related known derivatives as well as theoretical calculations of electronic circular dichroism (ECD) spectra. A plausible biosynthetic pathway of 1 and 2 , associating to folate metabolism and the previously reported orychophragines A-C from Orychophragmus violaceus, is discussed.

Title: Bipolarins A-H, eight new ophiobolin-type sesterterpenes with antimicrobial activity from fungus Bipolaris sp. TJ403-B1
[Abstract] Bipolarins A-H ( 1-8 ), eight new tetracyclic ophiobolin-type sesterterpenes featuring a rare oxaspiro[4.4]nonane moiety, were isolated from cultures of fungus Bipolaris sp. TJ403-B1. Their structures and absolute configurations were elucidated by comprehensive spectroscopic analyses, single-crystal X-ray diffraction experiments, electronic circular dichroism and 13C NMR calculations. Additionally, compound 5 exhibited significant selective antimicrobial activity against Enterococcus faecalis with an MIC value 8 μg·mL-1.

Title: Anti-HIV lignans from Justicia procumbens
[Abstract] Twenty-one lignans including three new ones ( 1 , 2 and 13 ) were isolated from Justicia procumbens. The chemical structures of the new lignans were determined by spectroscopic means including 1D and 2D NMR analysis. These compounds were evaluated for their cytotoxic and anti-HIV activities. The new secoisolariciresinol dimethyl ether acetate ( 13 ) exhibited anti-HIV-1 activity with an IC50 value of 5.27 μmol·L-1 and a selective index (SI) value of 2.2. The known arylnaphthalene lignan procumbenoside A ( 3 ) and diphyllin ( 8 ) demonstrated inhibitory activity against HIV-1 with IC50 values of 4.95 (SI > 6.2) and 0.38 μmol·L-1 (SI=5.3), respectively.

Title: Clerodane diterpenoids with potential anti-inflammatory activity from the leaves and twigs of Callicarpa cathayana
[Abstract] Phytochemical investigation of the leaves and twigs of Callicarpa cathayana led to the isolation of six new clerodane diterpenoids, cathayanalactones A-F ( 1-6 ), together with seven analogues ( 7-13 ). Their structures were established by extensive NMR analyses together with experimental and calculated ECD spectra analyses. Compounds 1 , 2 , 3 , 7 and 11 showed inhibitory activities on lipopolysaccharide-induced nitric oxide production in RAW264.7 cells.

Title: Enantiomeric pairs of meroterpenoids from Rhododendron fastigiatum
[Abstract] Five pairs of optically pure meroterpenoid enantiomers ( 1a/1b-5a/5b ) and two known compounds ( 6 and 7 ) were isolated from Rhododendron fastigiatum. Compounds 1a/1b-5a/5b were resolved from naturally scalemic mixtures by chiral HPLC. Their structures were elucidated by spectroscopic methods, X-ray crystallographic experiments, and ECD analyses. Compounds 1a/1b , 2a/2b , 3b , 4a/4b , and 5a/5b were new meroterpenoids with different polycyclic systems. Two enantiomeric pairs ( 2a/2b and 3a/3b ), 6 , and 7 exhibited inhibitory effects on protein tyrosine phosphatase 1B (PTP1B) in vitro.

Title: Structural determination of eleven new preschisanartane-type schinortriterpenoids from two Schisandra species and structural revision of preschisanartanin J using NMR computation method
[Abstract] Nineteen preschisanartane-type schinortriterpenoids (SNTs), among which eleven ones were previously undescribed, were isolated from two Schisandra species, S. sphaerandra and S. rubriflora. Their structures were determined using 1D and 2D NMR spectroscopic analyses, NMR data comparison, quantum chemical calculation of NMR parameters, electronic circular dichroism (ECD), X-ray single crystal diffraction, and chemical derivation. Furthermore, structural re-examination of a few previously reported preschisanartane-type SNTs led to the structural revision of preschisanartanin J. Besides, it is suggested that the reported structures of arisanlactone D and schilancidilactone W should be re-checked. Finally, a few isolated SNTs were found to possess neurite outgrowth-promoting activities, and protective activities against neural injuries.

Title: Cangumycins A-F, six new angucyclinone analogues with immunosuppressive activity from Streptomyces
[Abstract] Cangumycins A-F ( 1-6 ), six new angucyclinone analogues, together with two known ones ( 7 and 8 ), were isolated from the fermentation broth of a soil-derived Streptomyces sp. KIB-M10. Structures of these compounds were elucidated via a joint use of spectroscopic analyses and single-crystal X-ray diffractions. Among them, cangumycins E ( 5 ) and F ( 6 ) share a C-ring cleaved backbone, and cangumycins B ( 2 ) and E ( 5 ) exhibit potent immunosuppressive activity (IC50 8.1 and 2.7 μmol·L-1, respectively) against human T cell proliferation at a non-cytotoxic concentration.