Nectar Fluorescence under Ultraviolet Irradiation.

Nectar, which fluoresces in the visible and absorbs in the ultraviolet spectrum when irradiated by ultraviolet light, occurs in many bee-pollinated plants. It is suggested that these characteristics function as direct visual cues by which bees can evaluate the quantities of nectar available. Thus, they assume an important role in pollination of the flowers and foraging efficiency of beers.

Phylogenetic analysis of Artemisia section Tridentatae (Asteraceae) based on sequences from the internal transcribed spacers (ITS) of nuclear ribosomal DNA.

Artemisia sect. Tridentatae is composed of 11 species of xerophytic shrubs, which dominate much of western North America. Sequences of the internal transcribed spacers (ITS) of nuclear ribosomal DNA were used to construct a phylogeny, examine circumscription of the section, resolve interspecific relationships, and test competing hypotheses on the origin of the section. The data support the monophyly of sect. Tridentatae, with the exclusion of A. bigelovii and A. palmeri-two historically, anomolous species. However, the ITS data provide insufficient variation to fully resolve interspecific relationships or to support major lineages within the Tridentata clade. Nuclear and chloroplast DNA phylogenies are discordant, which may be a result of interspecific gene flow and subsequent chloroplast capture, particularly related to the placement of A. filifolia and A. californica, in addition to A. bigelovii. Furthermore, the ITS data are in conflict with cpDNA data, providing equivocal evidence for competing hypotheses on the Old World vs. New World origin for the section and do not provide support for definitive subgeneric placement.

Constituents of rosaceous plants. I. Structure of new triterpenoids from Cowania mexicana.

In our search for possible anti-tumor-promoters, we carried out an investigation of the leaves and branches of Cowania mexicana D. DON (Rosaceae). Two new cucurbitane type triterpenes, 15-oxo-cucurbitacin F (3) and 15-oxo-23,24-dihydrocucurbitacin F (4), were isolated together with cucurbitacin F (1) and 23,24-dihydrocucurbitacin F (2). These triterpenes were inhibitorss of Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate, a well-known tumor-promoter. The structures of 3 and 4 were determined from 2D-NMR spectral data and difference NOE experiments.

Antitumor agents, 138. Rotenoids and isoflavones as cytotoxic constitutents from Amorpha fruticosa.

Eight cytotoxic compounds have been isolated from the CHCl3 extract of Amorpha fruticosa. One compound, 6'-O-D-beta-glucopyranosyldalpanol [10], is a new cytotoxic rotenoid. Another known rotenoid, 12 alpha beta-hydroxyamorphigenin [6], was first shown to exhibit extremely potent cytotoxicity (ED50 < 0.001 microgram/ml) in six neoplastic cell lines. In addition to these compounds, three isoflavones (afrormosin [1], 7,2',4', 5'-tetramethoxyisoflavone [2], 8-methylretusin [3]) and five rotenoids (amorphispironone [4], amorphigenin [5], dalpanol [7], 12a beta-hydroxydalpanol [8], and tephrosin [9]) were isolated. Compound 8 was isolated for the first time as a natural product from this plant. The structures of these compounds were established on the basis of spectral data; some were further confirmed by X-ray crystallographic analysis.

Studies on inhibitors of skin tumor promotion, XII. Rotenoids from Amorpha fruticosa.

As a part of screening studies for chemopreventive agents (anti-tumor-promoters), six North American plants belonging to the Amorpha genus were tested using an in vitro assay system. Of these plants, Amorpha fruticosa exhibited strong inhibitory effects on Epstein-Barr virus early antigen (EBA-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Also six rotenoids, amorphispironone [1], tephrosin [2], amorphigenin [3], 12a-hydroxyamorphigenin [4], 12a-hydroxydalpanol [5], and 6'-O-D-glucopyranosyldalpanol [6], were isolated from the leaves of A. fruticosa. Among these retenoids, 1 and 2 exhibited remarkable inhibitory effects of EBV-EA activation induced by TPA. Further, 1 and 2 exhibited significant anti-tumor-promotion effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test. These investigations suggested that these rotenoids might be valuable anti-tumor-promoters.

Antitumor agents, 135. Structure and stereochemistry of polacandrin, a new cytotoxic triterpene from Polanisia dodecandra.

A new dammarane triterpene, polacandrin [1], has been isolated from Polanisia dodecandra. The structure of 1 was established as 1 beta, 3 alpha, 12 beta, 25-tetrahydroxy-20(S),24(S)-epoxydammarane by chemical and spectroscopic methods, which included the concerted application of a number of 2D nmr techniques that involved 1H-1H COSY, HETCOR, NOESY, and long-range HETCOR. Single-crystal X-ray analysis of polacandrin pentahydrate verified the complete structure and stereochemistry. Polacandrin showed potent cytotoxicities against KB (ED50 = 0.60 microgram/ml), P-388 (ED50 = 0.90 microgram/ml), and RPMI-7951 (ED50 = 0.62 microgram/ml) tumor cells.

Antitumor agents, 154. Cytotoxic and antimitotic flavonols from Polanisia dodecandra.

Three flavonols, 5,3'-dihydroxy-3,6,7,8,4'-pentamethoxyflavone [1], 5,4'-dihydroxy-3,6,7,8,3'-pentamethoxyflavone [2], and quercetin 3-O-beta-D-glucopyranosyl-7-O-alpha-L-rhamnopyranoside [3], were isolated from Polanisia dodecandra. Compound 1 showed remarkable cytotoxicity in vitro against panels of central nervous system cancer (SF-268, SF-539, SNB-75, U-251), non-small cell lung cancer (HOP-62, NCI-H266, NCI-H460, NCI-H522), small cell lung cancer (DMS-114), ovarian cancer (OVCAR-3, SK-OV-3), colon cancer (HCT-116), renal cancer (UO-31), a melanoma cell line (SK-MEL-5), and two leukemia cell lines (HL-60 [TB], SR), with GI50 values in the low micromolar to nanomolar concentration range. This substance also inhibited rubulin polymerization (IC50 = 0.83 +/- 0.2 microM) and the binding of radiolabeled colchicine to tubulin with 59% inhibition when present in equimolar concentrations with colchicine. Compound 2 also showed cytotoxicity against medulloblastoma (TE-671) tumor cells with an ED50 value of 0.98 microgram/ml. Compound 1 appears to be the first example of a flavonol to exhibit potent inhibition of tubulin polymerization and, therefore, warrants further investigation as an antimitotic agent.