A new semi-quinonechalcone C-glycoside isocartormin along with cartormin and safflomin C were isolated from the water extract of Carthamus tinctorius L. The structure of isocartormin was determined by extensive analysis of HR-MS, 1D- and 2D NMR data, and by comparison with those of cartormin reported previously by our group. Isocartormin was identified as a diastereoisomer of cartormin with a reverse configuration at C-18.Isocartormin, a new semi-quinonechalcone C-glycoside, along with two known analogs, cartormin and safflomin C, were separated from the water extract of Carthamus tinctorius L. Isocartormin was identified as a diastereoisomer of cartormin with a reverse configuration at C-18 through detailed analysis of its spectroscopic and mass data.Download high-res image (281KB)Download full-size image

Two new lignan-iridoid glucoside diesters (2 and 3), together with their putative biosynthetic precursor 10-O-trans-caffeoyl-6α-hydroxyl-dihydromonotropein (1), were characterized from the leaves of Vaccinium bracteatum. Their planar structures and relative configuration were elucidated by spectroscopic measurements and DFT C NMR calculations, and their absolute configurations were determined by time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The plausible biosynthetic pathways of new compounds were also proposed.Download high-res image (130KB)Download full-size image

Birhodomolleins A–C (1–3), three novel diterpenoids dimerized from two grayanane diterpenes through an oxygen bridge, were isolated from the flowers of Rhododendron molle. Their structures were elucidated by interpretation of their 1D and 2D NMR and other spectroscopic data. Birhodomollein A (1) contains a rare chloro-substitution on one of the grayanane moieties. These are the first examples of dimeric diterpenes from the Ericaceae family.Download high-res image (146KB)Download full-size imageThe first examples of dimeric diterpenoids from the Ericaceae family, birhodomolleins A–C (1–3), which dimerized from two grayanane diterpenes through a COC bond, were isolated from the flowers of Rhododendron molle. Their structures were elucidated by interpretation of their 1D and 2D NMR and other spectroscopic data.

Three rare sesquiterpene lactone dimers, dicarabrol A (1), dicarabrone C (2) and dipulchellin A (3), were isolated from the whole plants of Carpesium abrotanoides. Their structures were elucidated by comprehensive analyses of NMR and MS spectroscopic data. The structure of dipulchellin A was further confirmed by single-crystal X-ray crystallography. Compounds 1 and 2 possessed an unusual carbon skeleton with two carabranolide moieties linking through a spirotetrahydrofuran ring, which was presumably formed by a [4 + 2] cycloaddition. Compound 3 was a [3 + 2] cycloaddition product of a guaianolide moiety and a carabranolide moiety linking through a cyclopentane ring. Their plausible biosynthetic pathways were also proposed. Compounds 1–3 showed moderate cytotoxicity against HL-60 cells with IC50 values of 8.7 ± 0.3, 8.2 ± 0.3 and 8.9 ± 0.4 μM, respectively.

•Four iridoid glucoside cyclodimers were characterized from Vaccinium bracteatum.•Their structures were elucidated by extensive analysis of spectroscopic data.•Their absolute configurations were determined by X-ray diffraction experiment.•They were presumably biosynthesized from two known iridoid glucoside monomers.Divaccinosides A–D (1–4), four rare iridoid glucoside cyclodimers in the truxillate forms, were characterized from the leaves of Vaccinium bracteatum. They were presumably biosynthesized from two known iridoid glucoside monomers, vaccinoside (5) and 10-O-trans-p-coumaroyl-6α-hydroxyl-dihydromonotropein (6), via a [2+2] cycloaddition reaction. The structures of the new compounds were established by comprehensive spectroscopic measurements, combined with chemical conversions and single crystal X-ray crystallographic analyses.Download high-res image (62KB)Download full-size image

•Two new sesquiterpene lactones along with six known analogs were isolated from A. anomala.•Their structures were determined on the basis of extensive spectroscopic analyses.•All compounds have been evaluated for their in vitro cytotoxicity.•Compounds 6 and 7 showed moderate inhibition against human cancer cell lines HepG2 and A549.Two new sesquiterpene lactones, 8α-acetoxy-1,10α-epoxy-2-oxo-guaia-3,11(13)-dien-12,6α-olide (1) and 13-acetoxy-1-oxo-4α-hydroxy-eudesman-2(11)-dien-12,6α-olide (2), along with six known analogs (3-8), were isolated from the whole plant of Artemisia anomala S. Moore. Their structures were elucidated by extensive analysis of spectroscopic data. Compounds 6 and 7 exhibited in vitro moderate cytotoxicity against A549 cells with IC50 values of 0.6 and 0.9 μM, and HepG2 cells with IC50 values of 5.4 and 3.0 μM, respectively.Download high-res image (208KB)Download full-size image

Ten new cassane-type diterpenoids, caesalbonducins D–F (1–3), 6-deacetoxybonducellpin B (4), 3-acetoxy-α-caesalpin (5), 2(3)-en-α-caesalpin (6), 1α-hydroxycaesalpinin J (7), 1α-hydroxy-6-decaetoxysalpinin J (8), 6α-hydroxycaesall M (9), and 6α-hydroxy-14(17)-dehydrocaesalpin F (10), along with eight known compounds (11–18), were isolated from the pericarps of Caesalpinia bonduc. Compounds 1–3 and 11 are methyl-migrated cassane-type diterpenoids with a 19(4→3)-cassane skeleton. The structures of 1–10 were elucidated on the basis of 1D and 2D NMR methods and other spectroscopic analysis. The neuroprotective effects of the isolated compounds were evaluated.

•A polyoxypregnane aglycone and four polyoxypregnane steroids were isolated from Marsdenia tenacissima.•The polyoxypregnane steroids are naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety.•Two of these compounds exhibited a wide spectrum of chemoresistance reversal activity.•Potential mechanisms were studied.A polyoxypregnane aglycone, 12β-O-acetyl-11α-O-isobutyryltenacigenin B, and four polyoxypregnane glycosides with a pachybionic acid ester moiety, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-d-allopyranosyl-(1→4)-β-d-oleandronyl)-11α-O-isobutyryltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-d-allopyranosyl-(1→4)-β-d-oleandronyl)-11α-O-tigloyltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-d-allopyranosyl-(1→4)-β-d-oleandronyl)-11α-O-2-methylbutyryltenacigenin B, and 12β-O-acetyl-3-O-(β-d-glucopyranosyl-(1→4)-6-deoxy-3-O-methyl-β-d-allopyranosyl-(1→4)-d-oleandronyl)-11α-O-tigloyltenacigenin B, were isolated from the canes of Marsdenia tenacissima, together with a disaccharide derivative. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations were further determined by X-ray crystallographic analysis. With the exception of the disaccharide derivative, all five compounds are unusual naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety. Two of these exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.A polyoxypregnane aglycone (1) and four polyoxypregnane steroids (2–5) possessing an open-chain sugar moiety were isolated from Marsdenia tenacissima. Compounds 3 and 4 exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.

Dicarabrones A and B, a pair of epimers possessing a new skeleton featuring a cyclopentane ring connecting two sesquiterpene lactone units, were isolated from the whole plant of Carpesium abrotanoides L. Their full structures were established on the basis of spectroscopic data and were further confirmed by single-crystal X-ray crystallography. They were presumably biosynthesized from two sesquiterpenoid monomers through a [3 + 2] cycloaddition. Dicarabrones A and B showed moderate effects on HL-60 cells with IC50 values of 9.1 and 8.2 μM, respectively.

Twelve new inositol derivatives, classified into myoinositol (1–6) and l-inositol (10–15) types, along with five known analogues were isolated from the whole plant of Inula cappa. The structures of the new compounds were established by extensive analysis of mass spectrometric and 1D and 2D NMR spectroscopic data. All the tested compounds showed anti-inflammatory activities against the production of NO in RAW264.7 macrophages stimulated by lipopolysaccharide, with IC50 values ranging from 7 to 23 μM.

A new polyoxypregnane aglycone, tenacigenin D (1), and seven new C21 steroid glycosides, tenacissimosides D–J (2–8), were isolated from the stems of Marsdenia tenacissima. Their structures were determined by interpretation of their 1D and 2D NMR and other spectroscopic data, as well as by comparison with published values for related known compounds. Compound 1 was found to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance through an inhibitory effect on P-gp with a similar potency to verapamil. In addition, compound 1 potentiated the activity of erlotinib and gefitinib in epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI)-resistant non-small-cell lung cancer cells.

Nine new, uncommon humulane-type sesquiterpenoids (1, 2, 4, 6–11), together with two known derivatives, were isolated from extracts of the plant Pilea cavaleriei subsp. crenata. The structures of these compounds were fully elucidated by extensive analyses of spectroscopic data (MS, 1D- and 2D-NMR), use of the Mosher method, and by X-ray crystallographic analysis, in combination with chemical conversions. An ene reaction was discovered during the chemical transformations, which might provide an explanation for the wide distribution of the allylic hydroperoxide group in natural products.

Eight new ent-labdane diterpenoids, mallonicusins A–H (1–8), were isolated from the stems of Mallotus japonicus. Their structures, including the absolute configurations, were determined by extensive analyses of spectroscopic data and the ECD spectra of the Pr(FOD)3 complex of substrates in CCl4. The absolute configuration of compound 1 was confirmed by single-crystal X-ray crystallography using Cu Kα radiation.

The isolation of the retinal isomers from all-trans-retinal was performed by flash countercurrent chromatography. In each separation, isomerization reaction solution of 200 mg all-trans-retinal could be loaded on a 1200 mL of high-speed countercurrent chromatographic column with 5 mm bore, eluted by a mobile phase flow rate of 25 mL/min, resulting in 63 mg of 11-cis-retinal, 24 mg of 13-cis-retinal and 26 mg of 9-cis-retinal with purities more than 95%. n-Hexane–acetonitrile (3:1) was used as the solvent system which possesses the advantages of simplicity, re-use of the solvent and multiple injections. This method could be used to prepare 13-cis-retinal, 11-cis-retinal and 9-cis-retinal for the photoisomerization investigation, such as the effect of 11-cis-retinal in the visual system.Highlights► Isomerization of all-trans-retinal produces cis-retinal isomers. ► Flash countercurrent chromatography can isolate the cis-retinal isomers. ► In each separation, 3 cis-retinal monomers are obtained. ► This separation is simple and provides excellent recovery. ► This method provides 3 cis-retinal monomers in a scale of 10-mg.

Dictamins A–C, the first known examples of apotirucallane-type trinortriterpenoids, were isolated from the root bark of Dictamnus dasycarpus. Their structures and relative configurations were elucidated on the basis of extensive NMR and single-crystal X-ray diffraction analyses. Such compounds might be the key C5 side chain intermediates for an alternative degradation process from protolimonoids (C8 side chain) to limonoids (C4 side chain), bridging an oxidative cleavage biogenetic pathway between these two classes of structurally diverse triterpenoids.

Three new germacranolides, ineupatolides A–C (1–3), together with six known sesquiterpenoids, were isolated from the aerial parts of Inula cappa (Buch.-Ham.) DC. The structures of new compounds were elucidated by 1D-, and 2D-NMR techniques including HMQC, HMBC, 1H–1H COSY and ROESY spectra. The known compounds were identified by spectroscopic data analyses and data comparison. Compound 2 was finally proved to be converted from 1 with the trace existence of acid. Compounds 2 and 5 showed moderate inhibitory activity against human leukemia cell line HL-60, while compounds 2, 5, 6, 7 and 9 exhibited no antiproliferative activities on human lung cancer cell line A549.Graphical abstractThree new germacranolide sesquiterpenes (1–3) and six known analogues were isolated from Inula cappa, and their structures were elucidated by detailed analyses of MS, 1D-, and 2D-NMR spectroscopic data. A chemical conversion took place between compounds 1 and 2 in the presence of acid.Highlights► Three new germacrane-type sesquiterpenes were reported from Inula cappa. ► Structural elucidations were carried out by analyzing spectroscopic data. ► A chemical conversion took place between compounds 1 and 2 with the existence of acid. ► No compounds showed antiproliferative activity on human lung cancer cell line A549.

Fifteen limonoids, meliatoosenins E–S (1–15), and 10 known compounds were isolated from the fruits of Melia toosendan. Their structures were elucidated on the basis of extensive spectroscopic methods including DEPT, HSQC, HMBC, 1H–1H COSY, and ROESY experiments. All the compounds were evaluated for antiproliferative activity using A-549 and HL-60 cell lines.Graphical abstractFifteen limonoids were isolated from the fruits of Melia toosendan, along with 10 known compounds. Their antiproliferative activities were evaluated against A-549 and HL-60 cell lines.Highlights► A systematic investigation on chemical constituents from the fruits of Melia toosendan. ► Fifteen limonoids and 10 known ones were isolated. ► All compounds were evaluated for antiproliferative activity against two cell lines.

Four new limonoids (1, 3, 4, 6), named meliatoosenins A−D, eight new euphane- and tirucallane-type triterpenoids (8−15), named meliasenins A−H, and 13 known compounds have been isolated from the stem bark of Melia toosendan. The structures of new compounds were established on the basis of 1D and 2D NMR experiments (1H−1H COSY, HSQC, HMBC, and ROESY).

Phytochemical investigation on the stem bark and wood of Trigonostemon chinensis led to the isolation of four new dinorditerpenoids, trigonostemons A−D (1, 3, 5, 6), a new phenanthrenone, trigonostemon E (7), and a new bisindole alkaloid, trigonostemon F (8). The structures were established by extensive spectroscopic methods. The absolute configurations of 1−6 were determined by X-ray crystallography, circular dichroism, quantum chemical TDDFT calculations, and chemical transformations. The relative configuration of 8 was confirmed by X-ray diffraction analysis.

A new iridoid glucoside, allamanoid (1), was isolated from the aerial parts of Allamanda neriifolia, together with three known glucosides, plumieride, protoplumericin, and nicotiflorin. Their structures were elucidated by 1D and 2D spectroscopic analyses, hydrolysis, and comparison with literature data.

Four new merrillianin-type sesquiterpenes, oligandrumins A−D (1−4), two new seco-prezizaane-type sesquiterpenes, veranisatins D and E (5 and 6), and a new phenylpropane glycoside, oligandrumin E (7), were isolated from the ethanol extract of pericarps of Illicium oligandrum, together with six known sesquiterpenoids and two phenylpropanoids. Their structures were established on the basis of extensive spectroscopic analyses. The structures of 1 and 2 were further confirmed by single-crystal X-ray diffraction experiments. Anislactone B (13) and the erythro form of anethole glycol (14) were shown to attenuate the damage induced by H2O2 in SH-SY5Y cells.

Four new 9,10-dihydrophenanthrenes, juncuenins A−D (1−4), three new phenanthrenes, dehydrojuncuenins A−C (5−7), and three known compounds were isolated from the whole plants of Juncus setchuensis. The structures of the new compounds were established on the basis of detailed 1D and 2D NMR studies.

Four cucurbitane glycosides, momordicosides Q, R, S, and T, and stereochemistry-established karaviloside XI, were isolated from the vegetable bitter melon (Momordica charantia). These compounds and their aglycones exhibited a number of biologic effects beneficial to diabetes and obesity. In both L6 myotubes and 3T3-L1 adipocytes, they stimulated GLUT4 translocation to the cell membrane—an essential step for inducible glucose entry into cells. This was associated with increased activity of AMP-activated protein kinase (AMPK), a key pathway mediating glucose uptake and fatty acid oxidation. Furthermore, momordicoside(s) enhanced fatty acid oxidation and glucose disposal during glucose tolerance tests in both insulin-sensitive and insulin-resistant mice. These findings indicate that cucurbitane triterpenoids, the characteristic constituents of M. charantia, may provide leads as a class of therapeutics for diabetes and obesity.

Protein tyrosine kinase (PTK) inhibitors represent emerging therapeutics for cancer chemoprevention. In our study, hematoxylin (26) was identified as one of the most remarkable c-Src inhibitors in an orthogonal compound-mixing library (32200 compounds) by using an ELISA-based automated high-throughput screening (HTS) strategy. Interestingly, hematoxylin was found to be an ATP competitive broad-spectrum PTK inhibitor in vitro, with IC50 values ranging from nanomolar to micromolar level. Further studies showed that such inhibition was associated with the PTK phosphorylation and subsequent downstream signaling pathways. The structure−activity relationship assessment of the PTK inhibitory potency of hematoxylin analogues isolated from Heamatoxylon campechianum was in good agreement with the result of concurrent molecular docking simulation: the catechol moiety in ring A and the hematoxylin-like three-dimensional structure were essential for c-Src-targeted activities. Hematoxylin and its natural analogues were substantially validated to function as a new class of PTK inhibitors.

In our systematical investigation on Chinese Meliaceae plants, the stems of Cipadessa baccifera collected in Yunnan province were studied. Two new tetranortriterpenoids, cipadessalide (1) and rubralin D (2), one new pregnane, 3β,4β-dihydroxy-2β-acetoxypregnan-16-one (3), and two new sesquiterpenoids, bacciferins A (4) and B (5), along with 10 known compounds were isolated. Their structures were elucidated by 1D and 2D NMR spectra and other spectroscopic studies, as well as chemical conversion.

Five new alkaloids, 6β-hydroxystemofoline (1), 16-hydroxystemofoline (2), neostemofoline (3), protostemodiol (4), and 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5), along with 10 known alkaloids, were isolated from stems and leaves of Stemona japonica. Their structures were elucidated by 1D and 2D NMR and other spectroscopic studies. The insecticidal activity of the agonist 16-hydroxystemofoline (2) and antagonist 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5) was demonstrated by electrophysiological in vitro tests on the insect nicotinic acetylcholine receptor and by in vivo screenings against relevant agricultural insect pests.

Four new abietane diterpenoids, fortunins A−D (1−4), and six new 18-hydroxymethylene abietane diterpenoids, fortunins E−J (5−10), along with 12 known diterpenoids, were isolated from the bark of Cryptomeria fortunei. The structures of new compounds were established on the basis of 1D and 2D NMR and other spectroscopic analyses.

Investigation of the roots of Stemona tuberosa afforded five minor constituents, stemoenonine (1), 9a-O-methylstemoenonine (2), oxystemoenonine (3), 1,9a-seco-stemoenonine (4), and oxystemoninine (5), along with the known compound stemoninoamide (6). Their structures were elucidated by 1D and 2D NMR spectra and other spectroscopic studies. Alkaloids 1, 2, and 6, as well as the representative stemoninine-type alkaloid, stemoninine (7), were screened for antitussive activity in the citric acid-induced guinea pig cough model. Compounds 6 and 7 exhibited strong antitussive activity after oral and intraperitoneal administrations.

Nine bis-9,10-dihydrophenanthrene and 9,10-dihydrophenanthrene/(dihydro)stilbene derivatives, including the new phochinenins G-L 1–6, were isolated from the whole plant of Pholidota chinensis. Their structures were elucidated on the basis of extensive spectroscopic investigations (1D, 2D NMR, and HR-EIMS). Owing to the sterically hindered rotation around the biaryl axis, some of these biaryl compounds can exist as a pair of enantiomers, but were isolated as racemates. Computed inversion barriers of selected atropisomeric derivatives suggested that phochinenins K 5, gymconpin C 7, and flavanthrin 9 have stable atropisomers. Their racemates were separated by HPLC on an optically active stationary phase, and were stereochemically characterized on-line by circular dichroism (CD) spectroscopy (LC-CD coupling), in conjunction with quantum-mechanics CD calculations.(aS)-8-(2-(3-Hydroxyphenethyl)-4-hydroxy-6-methoxyphenyl)-7-methoxy-9,10-dihydrophenanthrene-2,5-diolC30H28O6(−)-CD [310 nm]Absolute configuration: (aS)C30H26O6(aS)-1-(2,7-Dihydroxy-4-methoxy-9,10-dihydrophenanthren-1-yl)-4-methoxy-9,10-dihydrophenanthrene-2,7-diol(+)-CD [310 nm]Absolute configuration: (aS)

Eight labdane-type diterpenes, 7β,13S-dihydroxylabda-8(17),14-dien-19-oic acid (1), 12R,15-dihydroxylabda-8(17),13E-dien-19-oic acid (3c), 12R,15-dihydroxylabda-8(17),13Z-dien-19-oic acid (3d), 12R,13R,14S-trihydroxylabda-12,15-epoxy-8(17)-en-19-oic acid (4a), 12S,13S,14R-trihydroxylabda-12,15-epoxy-8(17)-en-19-oic acid (4b), 15-hydroxy-12-oxolabda-8(17),13E-dien-19-oic acid (5), 14R,15-dihydroxylabda-8(17),12Z-dien-19-oic acid (7a) and 14S,15-dihydroxylabda-8(17),12Z-dien-19-oic acid (7b), along with 20 known diterpenoids, were isolated from the pericarp of Platycladus orientalis. Their structures were unambiguously elucidated by NMR spectroscopic and single crystal X-ray diffraction analyses, as well as via chemical correlation conversion. NMR spectroscopic data of known isomers 8c and 8d were reported as a supplement to existing data.Eight labdane-type diterpenes along with 20 known diterpenoid compounds were isolated from the pericarp of Platycladus orientalis.

Three new dimeric sesquiterpenoids, chloramultilides B−D (1−3), along with 10 known sesquiterpenoids, were isolated from the whole plant of Chloranthus spicatus. Their structures were established by physical data (1D and 2D NMR, MS). The structure and absolute configuration of 1 was confirmed by X-ray crystallography. Compound 1 exhibited moderate in vitro antifungal activity.

Ethnopharmacological relevanceMultidrug resistance (MDR) of cancer is often associated with the overexpression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP-1) and breast cancer resistance protein (BCRP or ABCG2), in cancer cells, which facilitates the active efflux of a wide variety of chemotherapeutic drugs out of the cells. Marsdenia tenacissima is a traditional Chinese medicinal herb that has long been clinically used for treatment of cancers, particularly in combinational use with anticancer drugs. Polyoxypregnanes (POPs) are identified as main constituents of this herb, and three of them have been reported to exhibit P-gp modulatory effect and thus reverse MDR. Therefore, it is of great necessity to investigate more POPs that have potential to reverse transporters-mediated MDR.Aim of the studyWe aimed to identify POPs as the chemical basis responsible for circumventing ABC transporters-mediated MDR by M. tenacissima.Materials and methodsThe MDR reversal effects of M. tenacissima crude extract together with a series of isolated POPs were evaluated on several MDR cancer cell lines that overexpress P-gp, MRP1 or ABCG2. The activities of P-gp, MRP1 and ABCG2 were determined by the flow cytometry-based substrate efflux assay. Molecular docking of POPs to a three-dimensional human P-gp homology structure was also performed.ResultsThe crude extract of M. tenacissima was firstly found to circumvent P-gp-mediated MDR. Then, 11 polyoxypregnane compounds (POPs) isolated from this herb were found to overcome P-gp-, MRP1- and/or ABCG2-mediated MDR. Further mechanistic study delineated that the reversal of MDR by these POPs was due to significant increase in the intracellular concentrations of the substrate anticancer drugs via their inhibition of different ABC transporter-mediated efflux activities. Furthermore, molecular docking revealed that POPs with P-gp modulatory effect bound to P-gp and fitted well into the cavity between the alpha and beta subunit of P-gp via forming hydrogen bonds. In addition, several key structural determinants for inhibition of P-gp, MRP1 or ABCG2 by POPs were illustrated.ConclusionsOur findings advocated the rational use of M. tenacissima to enhance efficacies of conventional anticancer drugs in tumors with ABC drug transporters-mediated MDR. Furthermore, 11 POPs were found to contribute to MDR reversal effect of M. tenacissima via inhibition of different ABC efflux transporters.Download high-res image (176KB)Download full-size image

A new seco-kalmane-type diterpenoid, seco-rhodomollone (1), five new grayanane-type diterpenoids, rhodomollein XXI (2), 6-O-acetylrhodomollein XXI (3), 6,14-di-O-acetylrhodomollein XXI (4), rhodomollein XXII (5), and 2-O-methylrhodomollein XI (6), and two new kalmane-type diterpenoids, rhodomolleins XXIII (7) and XXIV (8), together with seven known compounds, were isolated from the flowers of Rhododendron molle collected in Guangxi Province, China. The absolute configurations of 1 and 3 were defined by single-crystal X-ray diffraction experiments. Compound 1 possesses an unprecedented 1,5-seco-kalmane skeleton presumably derived by cleavage of the C-1–C-5 bond of the kalmane skeleton. Compounds 2–4 represent the first examples from a natural source of grayanane-type diterpenoids with a chlorine substituent.

Nine new, uncommon humulane-type sesquiterpenoids (1, 2, 4, 6–11), together with two known derivatives, were isolated from extracts of the plant Pilea cavaleriei subsp. crenata. The structures of these compounds were fully elucidated by extensive analyses of spectroscopic data (MS, 1D- and 2D-NMR), use of the Mosher method, and by X-ray crystallographic analysis, in combination with chemical conversions. An ene reaction was discovered during the chemical transformations, which might provide an explanation for the wide distribution of the allylic hydroperoxide group in natural products.