Natural Products Chemistry Research 2006's Progress in China

Chinese Journal of Natural Medicines 6 (2008) 00700078

Chinese Journal of Natural Medicines

Natural Products Chemistry Research 2006’s Progress in China YE Yang*, LI Xi-Qiang, TANG Chun-Ping Department of Natural Products Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203 Available online 20 January 2008 [ABSTRACT] This article reviews the progresses made by Chinese scientists in the field of natural products chemistry in 2006. Selected compounds with unique structural features and/or promising bioactivities were described herein on the basis of structural types. [KEY WORDS] Natural products chemistry; Natural compounds; Research progress

[CLC Number] R284; R285

[Document code] A

[Article ID] 1672-3651(2008)01-0070-09



Currently, research and development of new drugs from natural resources in a systematic and strategic manner has become the global trend. Natural product derived medicines are widely used and account for more than 30% of therapeutic agents presently prescribed in clinics. Artemisinin derivatives and taxols are the two examples that highlighted this research area. Pharmaceutical industry as a whole has also paid more attention to novel biological activities of natural products. In 2006, Chinese scientists have made a great deal of efforts in natural products chemistry and continued to be one of the world driving forces in this field. As a result, their achievements have received significant international recognitions. For instance, seven out of the twenty most-cited articles in Journal of Natural Products in 2006 were contributed by Chinese authors. Professor Jun Zhou and Professor Jikai Liu of Kunming Institute of Botany, Chinese Academy of Sciences have published invited review articles in Chemical Review; Professor Renxiang Tan of Nanjing University, special editor of Natural Product Reports, has organized Chinese scientists to contribute a whole issue focusing on the research progresses in natural products chemistry in China. Due to the limitation of the length of this review, we focus only on some leads with novel structures/skeletons and/or interesting bioactivities from articles published in 2006 by Chinese scientists.

1

Terpenes

1.1

Hemiterpenes and Monoterpenes A new hemiterpenoid, (+)-(2R,3S)-2-chloro-3-hydroxy3-methyl-Ȗ-buty-rolactone (1), was isolated from the leaves [Received on] 08-Nov-2007 [*Corresponding author]YE Yang, Prof., Tel&Fax: 86-21-508 06726; E-mail: [email protected] Copyright©2008, China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

of Prinsepia utilis (Rosaceae)[1]. A two-ring monoterpene, linchuniinone (2), was isolated from the root of Lindera chunii (Lauraceae)[2].

1.2

Sesquiterpenes Chloranoside A and six new sesquiterpene glycosides were isolated from the whole plant of Sarcandra glabra (Chloranthaceae). These compounds exhibited pronounced hepatoprotective activities against D-galactosamine-induced toxicity in WB-F344 rat hepatic epithelial stem-like cells[3]. From Chloranthus multistachys (Chloranthaceae), a highly complex sesquiterpenoid dimer, chloramultilide A (3), was obtained[4]. Two guaianolides, chinensiolides D and E, were isolated from Ixeris chinensis (Compositae). The latter showed significant growth inhibitory activity against VA-13 malignant lung tumor cells with an IC50 value of 0.72 ȝmol·L1.[5] From the flowers of Inula britannica var. chinensis (Compositae), three new sesquiterpenes and four known sesquiterpene lactones were isolated. Among them, neobritannilactone B (4) and acetyl neobritannilactone B exhibited modest activities in assays for cytotoxicity as well as apoptotic ratio in human COLO 205, HT-29, HL-60, and AGS cancer cells[6]. Two rearranged sesquiterpenes, laurokamurenes A (5) and B (6), were obtained from the Chinese red alga Laurencia okamurai[7]. Five minor sesquiterpenes with novel carbon skeletons, such as compound 7, were isolated from the brown alga Dictyopteris divaricata[8]. Com pound 8, a new sesquiterpene from the rhizomes and roots of Valeriana fauriei (Valerianaceae), showed enhancing activity of nerve growth factor (NGF)-induced neurite outgrowth in PC-12D cells[9]. Three new sesquiterpene coumarins,

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isofeterin, lehmannolol and sinkianone, were isolated from the roots of Ferula teterrima and Ferula sinkiangensis (Umbelliferae)[10]. A sesquiterpene isocyamide with a spiro [5, 6] decane skeleton, 3-oxo- axisonitrile-3 (9), was isolated from the Chinese marine sponge Acanthella sp. [11].

Diterpenes Three dimeric ent-kauranoids, bisrubescensins A-C, were isolated from Isodon rubescens (Labiatae). Bisrubescensin C was considered to be the precursor of bisrubescensin B from the viewpoint of biosynthesis [12] . Maoecrystal Z, a diterpene from the leaves of Isodon eriocalyx, exhibited comparable inhibitory effect against human K562 leukemia, MCF7 breast and A2780 ovarian tumor cells with IC 50 values of 2.90, 1.63, and 1.45 ȝg·mL-1[13] and with camptothecin and paclitaxel as the positive controls. Parvifoline X, a rearranged ent-kaurane diterpenoid, and parvifoline Y (10), a 8,15-seco-ent-kaurane diterpenoid, were isolated from the leaves of Isodon parvifolius. Compound 10 showed significant cytotoxic activity against A549 cells with an IC50 value of 4.97 ȝmol·mL1 [14]. Three neo-clerodane diterpenoids, barbatins A (11), B and C, were isolated from the whole plant of Scutellaria barbata (Labiatae). These compounds showed significant in vitro cytotoxic activities against HONE-1 nasopharyngeal, KB oral epidermoid carcinoma and HT29 colorectal carcinoma cells[15]. Wallichanols A (12) and B (13), two rearranged trachylobane diterpenoids from the roots of Euphorbia wallichii (Euphorbiaceae), showed potent activities to block osteoclastogenesis in vitro[16]. From the roots of Euphorbia fischeriana, 17-acetoxyjolkinolide B (14) was obtaind, exhibiting potent cytotoxic activity to Ramos B cells with an IC50 value of 0.023 ȝg·mL1 [17] . Five cembrane diterpenoids, sarcrassins A (15), B-E, were isolated from the soft coral Sarcophyton crassocaule. They exhibited significant cytotoxic activities against KB cell lines[18]. Juncins R (16) and other nine briarane diterpenoids were isolated from the South China Sea gorgonian coral Junceella juncea. Thesecompounds showed potent antifouling activities against the larval settlement of barnacle Balanus amphitrite at nontoxic concentrations [19] . Yuanhuajine (17) and yuanhuagine (18), two daphne diterpene esters with potent inhibitory activities against DNA topo I, were isolated from Daphne genkwa (Thymelaeaceae). They represent new type of topo I inhibitors bearing different structures compared with known Topoisomerase I inhibitors[20].A phytochemical investigation on the bark of Erythrophleum fordii (Caesal-

piniaceae) led to the isolation of six cassaine diterpenoid amides, among which compounds 19 and 20 exhibited significant cytotoxic activities against human cancer cells[21]. 1.4 Iridoids Two iridoid glucoside tetramers, dipsanosides A and B, were isolated from Dipsacus asper (Dipsacaceae) as the firstly-reported iridoid tetramers with four glucosides[22]. Four C9-irioids, buergerinins B (21), C-E, were isolated from the roots of Scrophularia buergeriana (Scrophulariaceae) [ 2 3 ] . F r o m t h e r o o t s o f N e o p i c ro rh i z a scrophulariiflora (Scrophulariaceae), piscrocins D (22) was isolated as a new non-glycosidic iridoid, which displayed potent in vitro hepatoprotective activity for mice hepatocytes injured by CCl4[24].

1.3

1.5

Triterpenes From the roots of Ozoroa insignis (Anacardiaceae), 3Į,25-dihydroxy-24-(2-hydroxyethyl)-tirucall-8-en-21-oic acid was isolated as the second C-32 tirucallane-type triterpene reported in literatures [25] .Acanthopanaxoside C, isolated from the leaves of Acanthopanax senticosus (Araliaceae), exhibited significant pancreatic lipase inhibitory activity in vitro [ 2 6] .Two 9,19-cycloartane triterpene glycosides, asiaticosides A and B, were isolated from the roots and rhizomes of Actaea asiatica (Ranunculaceae). Both compounds showed notable cytotoxicity against HepG2 and MCF-7 cancer cells[27].Eight highly oxygenated triterpene glycosides, symplocososides L-S, were isolated from the roots of Symplocos chinensi (Symplocaceae) [28] .Two triterpenoid saponins, polygalasaponins E and H, were isolated from the aerial parts of Polygala japonica (Polygalaceae). They could significantly reduce the immobility status in forced swimming mice model[29] . Triterpenoids from the resin of Styrax tonkinensis (Styracaceae) exhibited antiproliferative and differentiation effects in human leukemia HL-60 cells[30].Julibroside J21 (23), a triterpenoid saponin with a xylopyranosyl moiety located at its C-21 side chain, was isolated from Albizia julibrissin (Leguminosae). It showed marked inhibitory effect against Bel-7402 cancer cell line at the concentration of 10 ȝg·mL-1 [31]. From Jaspis sp., the marine sponge collected from the South China Sea, two isomalabaricane-type compounds, jaspolides A (24) and B (25) were obtained[32]. 1.6 Nortriterpenes An isomalabaricane-type nortriterpene, jaspolides E (26), was isolated from Jaspis sp. [32] . Rubriflordilactones B (27), a highly unsaturated rearranged bisnortriterpenoid possessing a biosynthetically modified aromatic D-ring, was isolated from the leaves and stems of Schisandra rubriflora (Schisandraceae). It exhibited inhibitory activity against HIV-1 replication with low cytotoxicity[33]. Two nor triterpenoids with a diversity of highly oxygenated structure, sphenadilactones A (28) and B, were isolated from the leaves and stems of Schisandra sphenanthera (Schisandraceae)[34]. Four novel tetranortriterpenoids, xylogranatins A-D, with an

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1.7

unusual 9,10-seco skeleton were isolated from the seeds of Xylocarpus granatum (Meliaceae). Xylogranatin B (29) exhibited moderate inhibitory effect against P-388 cancer cell lines[35].From the fruit of the same species, xyloccensins Y (30) and other polyhydroxylated phragmalins were reported[36].Turrapubesins A (31) and B, two novel tetranortriterpenoids from the twigs and leaves of Turraea pubescens (Meliaceae), represent the first examples of halogenated and maleimide-bearing limonoids[37].Nine nortriterpene dilactones with an unprecedented rearranged pentacyclic skeleton were isolated from the leaves and stems of Kadsura longipedunculata (Schisandraceae). Among them, longipedlactone A (32), B, C, F, H showed significant in vitro cytotoxicity against A549, HT-29 and K562 cell lines[38].Lancifodilactones K (33) and other nortriterpenoids were isolated from the leaves and stems of Schisandra lancifolia (Schisandraceae) [39].

Others An isomalabaricane-type sesterterpenoid, jaspolides F (34), was isolated from Jaspis sp.[32]. Two unusual C17 diterpenoids, (+)-7-deoxynimbidiol and celahypodiol, were isolated from the stalks of Celastrus hypoleucus (Celastraceae). Both compounds showed antitumor activities against A549 and CNEI human tumor cells[40, 41] . Przewalskin A (35), a C-23 terpenoid with a 6/6/7 carbon ring skeleton, was isolated from Salvia przewalskii (Labiatae). This compound showed modest anti-HIV-1 activity. [42] A degraded sesquiterpene, (1Į, 4aĮ, 5Į, 7ȕ, 8aȕ)-5, 8a-dimethyl-decahydrona-phthalene-1, 4a, 7-triol (36), was isolated from the marine actinomycete Streptomyces sp. 0616208[43]. against the human nasopharyngeal epidermoid tumor KB cell line with an IC50 value of 16.0 ȝmol·L -1[47] .Two unprecedented C,C-linked dimericindolizidine alkaloids, flueggenines A (41) and B, were iso lated from the roots of Flueggea virosa (Euphorbiaceae). Compound 41 showed weak activity against P-388 cell line[48]. A securinega type alkaloid, (-)-15ȕ-ethoxy-14, 15-dihydro-viroallosecurinine (42), was isolated from Securinega suffruticosa (Euphorbiaceae)[49]. Five stemoninine-type alkaloids were isolated from the roots of Stemona tuberose (Stemonaceae) and the main constituent bisdehydrostemoninine displayed significant antitussive activity in the citric acid-induced guinea pig cough model[50]. Daphnilongerine (44), an unusual yuzurine- type alkaloid with an unprecedented fused pentacyclic skeleton, was isolated from the fruits of Daphniphyllum longeracemosum (Daphniphyllaceae)[51]. Daphniyunnines A-E were isolated from the stems and leaves of Daphniphyllum yunnanense (Daphniphyllaceae). Daphniyunnine D showed cytotoxicity against P-388 and A-549 tumor cell lines[52]. From the same species, yunnandaphnine E (45), a heptacyclic yuzuriminetype alkaloid with an oxazine ring, was also reported[53]. Calycilactone A was isolated from the leaves of Daphniphyllum calycillum (Daphniphyllaceae) as a Daph niphyllum alkaloid with a rearranged fused-hexacyclic ring system[54].

3

Lignans

Five lignans were isolated from the whole plant of Pep eromia pellucida (Piperacea). Among them, compound 46

Yang Ye, et al. /Chinese Journal of Natural Medicines 2008 6(1): 007078

showed growth inhibitory effects on HL-60, MCF-7 and Hela human cancer cell lines[55].Rubrisandrin A, a dibenzocyclo octadiene lignan from the fruits of Schisandra rubriflora (Schisandraceae), exhibited the most potent anti-HIV activity [56] .Gnetucleistol F (47) was isolated from the lianas of Gnetum cleistostachyum (Gnetaceae), and it showed mod erate inhibitory activities on TNF-ǂ and malondialdehyde with IC50 values of 1.03 and 6.36 ȝmol·L1, respectively[57]. Two neolignan glucosides, bidenlignasides A and B, were isolated

from the whole plant of Bidens parviflora (Compositae).They were found to inhibit histamine release from peritoneal exudate mast cells induced by antigen-antibody reaction with

IC50 values of 25.1 and 37.2 ȝmol·L1 respectively[58].

4

Coumarins

A dimeric coumarin, diseselin B (48), was isolated from the aerial parts of Clausena lenis (Rutaceae)[59]. Two dihydrocoumarin derivatives, compounds 49 and 50, were isolated from Aloe vera (Liliaceae). Both compounds showed antioxidant activity against superoxide and hydroxyl radicals,

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vibrans, was found to inhibit pancreatic lipase with an IC 50 value of 0.4 Pg/mL. [67] Dichotomains A and B (57), two highly oxygenated phenolic derivatives featured by a spirodilactone moiety in their structures, were isolated from the fronds of Dicranopteris dichotoma (Gleicheniaceae). [68] A dimeric phthalide Z,Zƍ-3,3ƍa, 7,7ƍa-diligustilide (58) was isolated from the roots of Angelica sinensis (Umbelliferae). [69] and only 49 exhibited immunomodulatory activity in relation to increasing the phagocytic activity and stimulating the production of superoxide anions in the oxygen respiratory burst of rat peritoneal macrophages[60].

5

Flavones

An apigenin-derived xanthine oxidase inhibitor (51) was isolated from Palhinhaea cernua (Category). This glycoside inhibits xanthine oxidase in a competitive-noncompetitive manner[61]. Four flavan-4-ol glycosides were isolated from the rhizomes of Abacopteris penangiana (Athyriaceae). Among them, abacopterins A (52) showed cytotoxic activity against HepG2 human hepatoma cells[62].

6

Steroids

Chemical investigation of the marine sponge Haliclona oculata resulted in the isolation of eight compounds, among which 53 exhibited significant cytotoxic activities against HL-60, A-549 and BEL-7402 tumor cells with IC50 values of 0.32, 0.47 and 0.73 ȝg·mL1, respectively[63]. Two pregnane glycosides were isolated from the roots of Stephanotis mucronata (Asclepiadaceae). Both of them displayed significant immunosuppressive activities in vitro. [64] New spirostanols, dracaenogenins A (54) and B were isolated from the red resin of Dracaen cochinchinensis (Liliaceae) [65]. Two C-21 steroidal glycosides, chekiangensosides A and B (55), were isolated from the roots of Cynanchum chekiangense (Asclepiadaceae). These two glycosides showed immunol ogical activities in vitro against concanavalin A (Con A)- and lipopolysaccharide (LPS)-induced proliferation of mice splenocytes[66].

8

Rourinoside (59) was isolated from the stems of Rourea minor (Rosaceae) and it showed notable antimalarial activities in vitro against Plasmodium falciparum clones D6 and W2[70]. Four biphenyl glycosides, fortuneanosides B-E, were isolated from the fruit of Pyracantha fortunean (Rosaceae). All of these compounds showed inhibitory activity against tyrosinase with IC50 values of 2.21, 0.45, 0.07 and 0.14 ȝmol·L-1, respectively[71]. Chaetopyranin (60) was isolated from Chaetomium globosum, an endophytic fungus derived from the marine red alga Polysiphonia urceolata. This benzaldehyde secondary metabolite exhibited moderate DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging activity[72]. Decaspirones G (61) and other spirobisnaphthalene derivatives were isolated from cultures of an isolate of the saprophytic fungus Helicoma viridis. These compounds showed modest antimicrobial activities[73]. Five compounds with activity against Helicobacter pylori, psoracorylifols A, B (62), C–E, were isolated from the seeds of Psoralea corylifolia (Leguminosae)[74].

9

7

Lactones

Vibralactone (56), an unusual fused ȕ-lactonetype metabolite from the cultures of the Boreostereum

Phenols

Stilbenes

Six phenanthrene derivatives were isolated from the tubers of Cremastra appendiculata (Orchidaceae). Among these compounds, 63 and 64 exhibited cytotoxic activity against A549, A2780, and Bel7402 human cancer cell lines[75].Dendrochrysanene (65), a phenanthene with a spirolactone ring was isolated from the stems of Dendrobium chrysanthum (Orchidaceae). This phenanthrene derivative was proved to suppress the mRNA level of TNF-a, IL8, IL10, and iNOS in murine peritoneal macrophages[76].Hopeanolin (66), an unusual resveratral trimer with an ortho-quinone nucleus, was isolated from the stem bark of Hopea exalat (Dipterocarpaceae). It demonstrated antifungal activity in the MIC value range 0.1-22.5 ȝg·mL1 [77].

Yang Ye, et al. /Chinese Journal of Natural Medicines 2008 6(1): 007078

10

Quinones

Three antitumor anthraquinone glycosides, lasianthuoside A-C, were isolated from the root of Lasianthus acuminat-

ribes (Myrsinaceae)[79].

11

Acidamides

Gracilarioside (69), characterized with unusual cyclopropane-containing alkyl chains, was isolated from the red alga Gracilaria asiatica. It showed mildly cytotoxicity against the human A375-S2 melanoma cell line[80]. S632A3 (70), an antibiotic from a cultured broth of Streptomyces hygroscopicus S632, showed potent cytotoxic activity against S180, Hepatoma 22 and Lewis human cancer cell lines[81].

12

issimus (Rubiaceae)[78]. An unusual nitrogencontaining 3-alkyl-1, 4-benzoquinone derivative (67) and a gomphilactone derivative (68) were isolated from the roots of Embelia

Thiophenes

Xanthopappins A-C, thiophene derivatives from Xanthopappus subacaulis (Compositae), exhibited significant larvae of the Asian tiger mosquito with LC50 values of 0.71, 0.53, and 0.95 ȝg·mL-1, respectively, but in the dark only xanthopappin B (71) showed such activity with an LC50 value of 5.1 ȝg·mL-1[82]. From the roots of Echinops latifolius (Compositae), 5-(3-hydroxymethyl-3-isovaleroyloxyprop-1ynyl) -2, 2ƍ-bithiophene (72) was obtained[83].

13

Others

A long-chain fatty acid ester, (9E)-8,11,12- trihydroxyoc tadecenoic acid methyl ester, was obtained from the stems of Sambucus williamsii (Caprifoliaceae). This compound showed stimulating effects on alkaline phosphatase activity of the osteoblastic UMR106 cell about 1.5 fold at concentration of 30ȝmol·L-1 but had no effects on cell proliferation[84]. A cytotoxic compound, 24-ȕ-n-propyl-O-manoalide (73), was isolated from Luffariella sp. It exhibited significant growth inhibitory activity against HCT-116 cell line with an IC50 value of 0.32ȝg·mL-1 [85]. A cyclopeptide, arenariphilin C, and a dipeptide, arenariphilin D, were isolated from the roots of Arenaria oreophila (Caryophyllaceae)[86].

Yang Ye, et al. /Chinese Journal of Natural Medicines 2009, 6(1): 007078 Acanthella sp. [J]. J Asian Nat Prod Res, 2006, 8 (6): 579-584. [12] Huang SX, Xiao WL, Li LM, et al. Bisrubescensins A-C: three new dimeric ent ǂ Kauranoids isolated from Isodon rubescens [J]. Org Lett, 2006, 8 (6): 1157-1160.

14

Biotransformation

A ketone derivative of artemisinin, artemisitone-9 (74), produced by the biotransformation of cultured Streptomyces griseus ATCC 13273, exhibited antimalarial activity against P. falciparum FCC-1/HN strain with an IC50 value of 29.3 ng·mL1 [87].

[13] Han QB, Cheung S, Tai J, et al. Maoecrystal Z, a cytotoxic diterpene from Isodon eriocalyx with a unique skeleton [J]. Org Lett, 2006, 8 (21): 4727-4730. [14] Li LM, Li GY, Xiao WL, et al. A new rearranged and a new seco-ent-kaurane diterpenoids from Isodon parvifolius [J]. Tetrahedron Lett, 2006, 47: 5187-5190. [15] Dai SJ, Tao JY, Liu K, et al. neo-Clerodane diterpenoids from Scutellaria barbata with cytotoxic activities [J]. Phytochemistry, 2006, 67: 1326-1330. [16] Pan L, Zhou P, Zhang XF, et al. Skeleton-rearranged pentacyclic diterpenoids possessing a cyclobutane ring from Euphorbia wallichii [J]. Org Lett, 2006, 8 (13): 2775-2778. [17] Wang YB, Huang R, Wang HB, et al. Diterpenoids from the roots of Euphorbia fischeriana [J]. J Nat Prod, 2006, 69: 967-970.

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