Identification of Insect-Deterrent Metabolites from Acremonium masseei strain CICY026, a Saprophytic Fungus from a Sinkhole in Yucatán.

Micromycetes from unexplored sources represent an opportunity to discover novel natural products to control insect pests. With this aim, a strain of Acremonium masseei CICY026 isolated from a tropical sinkhole was identified, cultured on fermented rice, and its ethyl acetate extract (EAE) was evaluated against three serious phytophagous insects (Bemisia tabaci, Myzus persicae, and Rhopalosiphum padi). DNA from A. masseei CICY026 was used to confirm its identity. EAE caused settling inhibition (SI) of M. persicae and R. padi (67.5% and 75.3%, respectively). Bioassay-guided fractionation of the active EAE led to the isolation of a novel metabolite, named hexahydroacremonintriol (1), and of acremonin A glucoside (2). The structures of 1 and 2 were determined using IR, one- and two-dimensional NMR, HRMS, and confirmed by theoretical data. The aphid M. persicae was noticeably sensitive to 1 and 2 (SI: 55.6% and 67.2%, respectively), whereas R. padi was only slightly affected by 1 (SI: 59%). This new knowledge about mycobiota from these special sinkhole ecosystems will inform the development of new biorational pesticides.

Phenylpropanoid glycoside analogues: enzymatic synthesis, antioxidant activity and theoretical study of their free radical scavenger mechanism.

Phenylpropanoid glycosides (PPGs) are natural compounds present in several medicinal plants that have high antioxidant power and diverse biological activities. Because of their low content in plants (less than 5% w/w), several chemical synthetic routes to produce PPGs have been developed, but their synthesis is a time consuming process and the achieved yields are often low. In this study, an alternative and efficient two-step biosynthetic route to obtain natural PPG analogues is reported for the first time. Two galactosides were initially synthesized from vanillyl alcohol and homovanillyl alcohol by a transgalactosylation reaction catalyzed by Kluyveromyces lactis ß-galactosidase in saturated lactose solutions with a 30%-35% yield. To synthesize PPGs, the galactoconjugates were esterified with saturated and unsaturated hydroxycinnamic acid derivatives using Candida antarctica Lipase B (CaL-B) as a biocatalyst with 40%-60% yields. The scavenging ability of the phenolic raw materials, intermediates and PPGs was evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) method. It was found that the biosynthesized PPGs had higher scavenging abilities when compared to ascorbic acid, the reference compound, while their antioxidant activities were found similar to that of natural PPGs. Moreover, density functional theory (DFT) calculations were used to determine that the PPGs antioxidant mechanism proceeds through a sequential proton loss single electron transfer (SPLET). The enzymatic process reported in this study is an efficient and versatile route to obtain PPGs from different phenylpropanoid acids, sugars and phenolic alcohols.

Phytotoxic activity of bibenzyl derivatives from the orchid Epidendrum rigidum.

A whole plant chloroform-methanol extract of the orchid Epidendrum rigidum inhibited radicle growth of Amaranthus hypochondriacus seedlings (IC50 = 300 microg/mL). Bioassay-guided fractionation furnished four phytotoxins, namely, gigantol (1), batatasin III (2), 2,3-dimethoxy-9,10-dihydrophenathrene-4,7-diol (9), and 3,4,9-trimethoxyphenanthrene-2,5-diol (11), along with the known flavonoids apigenin, vitexin, and isovetin and the triterterpenoids 24,24-dimethyl-9,19-cyclolanostane-25-en-3beta-ol (14) and 24-methyl-9,19-cyclolanostane-25-en-3beta-ol (15). Stilbenoids 1, 2, 9, and 11 inhibited radicle growth of A. hypochondriacus with IC50 values of 0.65, 0.1, 0.12, and 5.9 microM, respectively. Foliar application of gigantol (1) at 1 microM to 4 week old seedlings of A. hypochondriacus reduced shoot elongation by 69% and fresh weight accumulation by 54%. Bibenzyls 1 and 2, as well as synthetic analogues 4'-hydroxy-3,3',5-trimethoxybibenzyl (3), 3,3',4',5-tetramethoxybibenzyl (4), 3,4'-dihydroxy-5-methoxybibenzyl (5), 3'-O-methylbatatasin III (6), 3,3',5-trihydroxybibenzyl (7), and 3,4',5-trihydroxybibenzyl (8), were tested for phytotoxicity in axenic cultures of the small aquatic plant Lemna pausicostata. All bibenzyls derivatives except 7 and 8 inhibited growth and increased cellular leakage with IC50 values of 89.9-180 and 89.9-166 microM, respectively. The natural and synthetic bibenzyls showed marginal cytotoxicity on animal cells. The results suggest that orchid bibenzyls may be good lead compounds for the development of novel herbicidal agents.

Spasmolytic effects, mode of action, and structure-activity relationships of stilbenoids from Nidema boothii.

A CH(2)Cl(2)-MeOH (1:1) extract prepared from the whole plant of Nidema boothii inhibited spontaneous contractions (IC(50) = 6.26 +/- 2.5 microg/mL) of the guinea-pig ileum. Bioassay-guided fractionation of the active extract led to the isolation of the novel spiro compound 1, which was given the trivial name nidemone, and the new dihydrophenanthrene 3, characterized as 1,5,7-trimethoxy-9,10-dihydrophenanthrene-2,6-diol. In addition, the known stilbenoids aloifol II (2), 1,5,7-trimethoxyphenanthrene-2,6-diol (4), ephemeranthoquinone (5), gigantol (6), ephemeranthol B (7), 2,4-dimethoxyphenanthrene-3,7-diol (8), lusianthridin (9), and batatasin III (10) were obtained. The isolates were characterized structurally by spectroscopic data interpretation. Compounds 2-6, 9, and 10 induced notable concentration-dependent inhibition of the spontaneous contractions of the guinea-pig ileum with IC(50) values that ranged between 0.14 and 2.36 microM. Bibenzyl analogues 23-35 were synthesized and tested pharmacologically. The results indicated that for maximum spasmolytic activity the bibenzyls should have oxygenated substituents on both aromatic rings; on the other hand, methylation of free hydroxyl groups as well as the increment of oxygenated groups in relation to compounds 6 and 10 decreased the smooth muscle relaxant activity. It was also demonstrated that bibenzyls 6 and 10 might exert their spasmolytic action not only by a nitrergic mechanism but also by inhibiting CaM-mediated processes.