Plant antitumor agents. 31. The calycopterones, a new class of biflavonoids with novel cytotoxicity in a diverse panel of human tumor cell lines.

Three new biflavonoids to which we have accorded the trivial names calycopterone (1), isocalycopterone (2), and 4-demethylcalycopterone (3) and the known flavone 4',5-dihydroxy-3,3',6,7-tetramethoxyflavone (4) were isolated as cytotoxic constituents from the flowers of Calycopteris floribunda Lamk. (Combretaceae). Compounds 1-3 showed a wide range of activity against a panel of solid tumor cell lines. Among the biflavonoids, calycopterone (1) is the major constituent.

Cardiac glycosides of Beaumontia brevituba and B. murtonii.

Cardiac glycosides from Beaumontia brevituba and B. murtonii were examined. Gentiobiosyl-beta-D-cymaroside and gentiobiosyl-alpha-L-cymaroside of digitoxigenin were isolated from the seeds, unripe fruits, and leaves of B. brevituba, and the leaves of B. murtonii. Oleandrigenin and/or delta 16-digitoxigenin glycosides having the same sugar moieties were not isolated from the leaves of B. brevituba but from the leaves of B. murtonii as well as the seeds of B. brevituba.

An azaanthracene alkaloid from Polyalthia suberosa.

An azaanthracene alkaloid, 1-aza-9,10-dimethoxy-4-methyl-2-oxo-1,2-dihydroanthracene (kalasinamide) has been isolated from the stems of Polyalthia suberosa. In addition, the known N-trans-feruloyltyramine and N-trans-coumaroyltyramine are also reported from the same source. The structures were elucidated by spectroscopic methods.

Flavonol glycosides from Dasymaschalon sootepense.

Two novel flavonol glycosides have been isolated from a methanolic extract of Dasymaschalon sootepense leaves. They are the 3'-neohesperidoside and 3'(6G-alpha-rhamnosylneohesperidoside) of quercetin 3,7-dimethyl ether.

Xanthones from the twigs of Mammea siamensis.

1,2-Dimethoxy-5-hydroxyxanthone, a new xanthone, was isolated from the twigs of Mammea siamensis, in addition to six known xanthones (5-hydroxy-1-methoxy-, 1,3-dimethoxy-5-hydroxy-, 2,5-dihydroxy-1-methoxy-, 1,7-dihydroxy-, 1,3,7-trihydroxy- and 3,5-dihydroxy-1-methoxyxanthone). Structures for these compounds were deduced from their spectral data.

Limonoids from Azadirachta excelsa.

Activity-directed fractionation of a stem extract of Azadirachta excelsa using KB (human oral epidermoid carcinoma) cells led to the isolation of four meliacin-type limonoids. Two of these constituents were novel, namely, 2,3-dihydronimbolide and 3-deoxymethylnimbidate, and these were purified along with the known compounds, nimbolide and 28-deoxonimbolide. The structures of the new compounds were determined by spectroscopic methods. Nimbolide and 28-deoxonimbolide were broadly cytotoxic when evaluated against a panel of human cancer cell lines, while the two novel compounds were inactive in this regard. The defection of nimbolide and 28-deoxonimbolide as cytotoxic constituents was facilitated by an electrospray LC/MS dereplication procedure.

Evaluation of anti-HSV-2 activities of Barleria lupulina and Clinacanthus nutans.

Barleria lupulina Lindl. and Clinacanthus nutans (Burm. f.) Lindau, both belonging to the family Acantaceae, are well-known medicinal plants used in Thai folklore medicine. Virucidal effects of organic extracts of these two plants against herpes simplex virus type 2 strain G, HSV-2 (G), the standard HSV-2 strain were noted. The extracts were assessed for intracellular activities against HSV-2 (G) and five clinical HSV-2 isolates. B. lupulina extract exhibited activity against all five isolates but not the standard strain while that of C. nutans did not show any activity against these viruses as determined by plaque inhibition assay. When the activities were verified by yield reduction assay, anti-HSV-2 activities of B. lupulina extract were observed against HSV-2 (G) as well. The results suggest a therapeutic potential of B. lupulina but not C. nutans against HSV-2.

A sensitive assay for anti-HIV-1 drug discovery in a biological safety level-2 laboratory.

Studies involving infectious, wild type HIV-1 must be performed under strict BSL-3 practice. We have employed a defective (deltaTat/Rev)MC99 and cloned 1A2 line, ie, mutated HIV-1 and Tat/Rev transfected cells to verify anti-HIV-1 activity in a BSL-2 laboratory. A number of extracts from various parts of 11 species of plants were studied. Results were correlated with those of an anti-HIV-1 reverse transcriptase (RT) assay.

A phytochemical investigation of Homalium ceylanicum.

Vacciniin [4] (6-O-benzoyl-D-glucopyranoside) and two new benzenoid glucosides, homaloside A [1] (1''-O-benzyl-3''-O-benzoyl-alpha-L-arabinopyranosyl(1'''-->4'')- beta-D-glucopyranoside) and homaloside D [2] [1-(1'-hydroxy-6'-oxocyclohex-2'-ene-carboxymethyl)- 5-hydroxyphenyl-6''-O-benzoyl-beta-D-glucopyranoside], were isolated from the n-BuOH fraction of Homalium ceylanicum (Flacourtiaceae). A novel cyclohexenone carboxylic acid ester, 1-hydroxy-6-oxocyclohex-2-enoic acid methyl ester [3], was also isolated from this fraction. The structures were elucidated by chemical and nmr (COLOC, FLOCK, and selective INEPT) techniques.

New lignans from Anogeissus acuminata with HIV-1 reverse transcriptase inhibitory activity.

Anolignan A [1] and anolignan B [3] are new dibenzylbutadiene lignans isolated from Anogeissus acuminata. Compounds 1 and 3 were identified as the active HIV-1 reverse transcriptase (RT) inhibitory constituents of this plant obtained by bioassay-guided fractionation. Compound 3, which was very weakly active when tested alone, showed high activity when combined with 1. The activity of 1 was likewise enhanced in the presence of 3. A concave isobole obtained from a plot of data derived from assays with 1 and 3 in combination indicated their synergistic effects. Another new lignan, anolignan C [5], and a known lignan, (-)-secoisolariciresinol [10], were also isolated from this plant. Compounds 5 and 10 did not have activity against HIV-1 RT. Compounds 1, 3 and 5 were either weakly cytotoxic or noncytotoxic when tested in various cancer cell lines. The structures of 1-5 and 10 were established by spectroscopic methods, especially by 1D and 2D nmr experiments.

2-substituted furans from Polyalthia suberosa.

Two new 2-substituted furans, 1-(2-furyl)pentacosa-16,18-diyne and 23-(2-furyl)tricosa-5,7-diynoic acid, have been isolated from stems of Polyalthia suberosa. The structures were assigned by spectroscopic methods. The two compounds together with the previously reported kalasinamide, N-trans-feruloyltyramine and N-trans-coumaroyltyramine showed anti-HIV activities.

Three non-phenolic diarylheptanoids with anti-inflammatory activity from Curcuma xanthorrhiza.

Bioassay-guided fractionation of a hexane extract of the rhizomes of Curcuma xanthorrhiza Roxb. (Zingiberaceae) led to the isolation of three non-phenolic diarylheptanoids, identified mainly by high-field 1H-NMR as trans-trans-1,7-diphenyl-1,3-heptadien-4-one (alnustone), trans-1,7-diphenyl-1-hepten-5-ol, and trans,trans-1,7-diphenyl-1,3-heptadien-5-ol. The latter is reported for the first time as a plant constituent. Germacrone, curzerenone, and cinnamaldehyde were also isolated and identified. The three diarylheptanoids all exerted significant anti-inflammatory activity in the assay of carrageenin-induced hind paw edema in rats.

Cytotoxic activity of cardenolides from Beaumontia brevituba stems.

Five known cardenolides, digitoxigenin (1), oleandrigenin (2), digitoxigenin alpha-L-cymaroside (3), digitoxigenin beta-gentiobiosyl-alpha-L-cymaroside (4), and delta 16-digitoxigenin beta-D-glucosyl-alpha-L-cymaroside (5), were isolated from the stems of Beaumontia brevituba Oliver by cytotoxicity-directed fractionation monitored by a cultured human lung cancer cell line. The cytotoxic activity of these compounds was evaluated with a panel of twelve human and murine cancer cell lines. The lignan glycoside, syringaresinol beta-D-glucoside, was obtained for the first time in the form of its levo-enantiomer.

Plant anticancer agents, L. cytotoxic triterpenes from Sandoricum koetjape stems.

A new ring-A secotriterpene, koetjapic acid [1], and five known compounds, 3-oxo-olean-12-en-29-oic acid [2] (a novel natural product), katonic acid [3], (-)-alloaromadendrene, (-)-caryophyllene oxide, and (+)-spathulenol, have been isolated and characterized from a cytotoxic Et2O-soluble extract of Sandoricum koetjape stems. Of these compounds, 2 and 3 demonstrated significant cytotoxic activity against cultured P-388 cells (ED50 values of 0.61 and 0.11 microgram/ml, respectively). Significant, albeit less intense, cytotoxicity was also observed with a variety of cultured human cancer cells. The 13C-nmr chemical shifts of these triterpenes were assigned unambiguously using selective INEPT nmr experiments. Aside from compounds 2 and 3, these substances were not toxic with cultured cells.

Plant anticancer agents, XLVIII. New cytotoxic flavonoids from Muntingia calabura roots.

From a cytotoxic Et2O-soluble extract of Muntingia calabura roots, twelve new flavonoids were isolated, constituting seven flavans 1-7, three flavones 8, 10, and 12, and two biflavans 9 and 11. The structures of compounds 1-12 were established by the interpretation of spectral data, with the nmr assignments of these constituents being based on 1H-1H COSY, 1H-13C HETCOR, and selective INEPT experiments. This is the first report of the occurrence of 7,8-di-O-substituted flavans, biflavans, and flavones. Most of the isolates demonstrated cytotoxic activity when tested against cultured P-388 cells, with the flavans being more active than the flavones. Furthermore, certain of these structurally related flavonoids exhibited somewhat selective activities when evaluated with a number of human cancer cell lines.

New compounds with DNA strand-scission activity from the combined leaf and stem of Uvaria hamiltonii.

Two flavanones, hamiltones A (1) and B (2), an aurone, hamiltrone (3), a chalcone, hamilcone (4), and a tetrahydroxanthene, hamilxanthene (5), were isolated from Uvaria hamiltonii extracts guided initially by fractionation based on DNA strand-scission and/or 9KB cytotoxicity assays. Compounds 2-5 have not been reported previously, while 1 is new as a natural product. Structural assignments were made based on extensive spectroscopic measurements. Compounds 1-3 were inactive in the 9KB cytotoxicity assay, with compounds 4 and 5 having weak activity. In the DNA strand-scission assay, 3 was the most active compound found in the DNA strand-scission assay, being 10 times more potent than 1 or 2. Compound 4 was only weakly active, and 5 was inactive.

Novel cytotoxic acylated oligorhamnosides from Mezzettia leptopoda.

Activity-guided fractionation of a stem extract of Mezzettia leptopoda using human oral epidermoid carcinoma (KB) cells led to the isolation of seven highly acylated oligorhamnosides. Four of these constituents are novel, namely, n-octyl 2-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-2, 4-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 8) (1); n-octyl 2, 3-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 9) (2); n-octyl 2, 4-di-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-rh amnopyranoside (mezzettiaside 10) (3); and n-octyl 2,3, 4-tri-O-acetyl-alpha-L-rhamnopyranosyl-(1-->3)-4-O-hexanoyl-alpha-L-r hamnopyranoside (mezzettiaside 11) (4). Three known compounds were identified as mezzettiasides 2 (5), 3 (6), and 4 (7), respectively, previously isolated from this same plant. The structures of novel compounds 1-4 were determined by spectroscopic methods. All the isolates were evaluated against a panel of human cancer cell lines in this study, and compounds 1-2 and 4-7 were found to be weakly cytotoxic toward KB and/or human colon and lung cancer cell lines.

Lupane derivatives from Lophopetalum wallichii with farnesyl protein transferase inhibitory activity.

Chloroform-soluble extracts of the stems and of the mixed stems and stem bark of Lophopetalum wallichii were found to be inhibitory in a farnesyl protein transferase (FPTase) bioassay system. During the course of activity-guided fractionation, the known lupane-type triterpenes, ochraceolide A (1), ochraceolide B (2), betulin, and lupeol and the new lupane lactone, dihydro ochraceolide A (4), were isolated. The stereochemistry of the epoxide group of ochraceolide B (2) was determined by preparation of both epoxide isomers [2, and the new semisynthetic derivative, 20-epi-ochraceolide B (3)] from 1. The structure of 4 was established by reduction of 1 with sodium borohydride. Compounds 1 and 2 exhibited significant inhibitory activity in the FPTase assay (IC50 values of 1.0 and 0.7 microgram/mL, respectively). Lupeol was found to be weakly active (IC50 65.0 micrograms/mL) in this test system, whereas no significant inhibition was detected for betulin or compounds 3 or 4. When evaluated against a panel of human cancer cells in culture, compounds 1 and 4 were modestly cytotoxic. Compounds 2 and 3 were not active in the panel.