santonin and lumisantonin

Faced with the need to develop herbicides with different modes of action on account of weed resistance to existing herbicides, the sesquiterpene lactones can be the starting point in the search for new bioactive compounds. Lumisantonin and five novel amides have been evaluated against two monocotyledons and three dicotyledons.. An efficient and versatile synthesis of lumisantonin and the five novel amides has been accomplished from readily available α-santonin. These compounds were subjected to evaluation for their biological activity against Sorghum bicolor (sorghum), Allium cepa (onion), Cucumis sativus (cucumber), Solanum lycopersicum (tomato) and Bidens pilosa (beggartick). Lumisantonin has inhibited the development of the aerial parts of sorghum and onion by 76 and 67% at 1000 µM respectively. One of the novel amides has prevented the growth of shoots and radicles of sorghum by 80 and 71% at 1000 µM respectively.. All of the tested compounds have been found to exhibit promising seed germination inhibition. We can conclude that lumisantonin was on average the most lethal against all plant species evaluated; however, two of the novel amides have exhibited inhibition selectivity against monocotyledons when compared with dicotyledons. © 2015 Society of Chemical Industry.

Topics: Adamantane; Amides; Aminobenzoates; Anilides; Crops, Agricultural; Herbicides; Plants; Santonin

The CASSCF and CASPT2 methodologies have been used to explore the potential energy surfaces of lumisantonin in the ground and low-lying triplet states along the photoisomerization pathways. Calculations indicate that the (1)(nπ*) state is the accessible low-lying singlet state with a notable oscillator strength under an excitation wavelength of 320 nm and that it can effectively decay to the (3)(ππ*) state through intersystem crossing in the region of minimum surface crossings with a notable spin-orbital coupling constant. The (3)(ππ*) state, derived from the promotion of an electron from the π-type orbital mixed with the σ orbital localized on the C-C bond in the three-membered alkyl ring to the π* orbital of conjugation carbon atoms, plays a critical role in C-C bond cleavage. Based on the different C-C bond rupture patterns, the reaction pathways can be divided into paths A and B. Photolysis along path A arising from C1-C5 bond rupture is favorable because of the dynamic and thermodynamic preferences on the triplet excited-state PES. Path B is derived from the cleavage of the C5-C6 bond, leading first to a relatively stable species, compared to intermediate A-INT formed on the ground state PES. Accordingly, path B is relatively facile for the pyrolytic reaction. The present results provide a basis to interpret the experimental observations.

Topics: Models, Molecular; Photochemistry; Santonin

1,2-Dihydrosantonin is the first stable product in the degradative pathway of alpha-santonin by Pseudomonas cichorii S. Its formation is catalyzed by an oxidoreductase, which is NADH or NADPH dependent and has an apparent Km value of 66.66 microM for santonin and 44.33 microM for NADH. The enzyme activity is stable at pH 6.0, 7.0, and 8.0, and is not affected by EDTA and divalent metal ions. It is postulated that the enzymic reduction of santonin occurs via formation of a transient zwitterionic intermediate, which undergoes nonenzymatic 1,4-sigmatropic rearrangement to yield lumisantonin during the solvent extraction process. Lumisantonin is, thus, not a true metabolic intermediate but an artifact.

Topics: Biodegradation, Environmental; Chemical Phenomena; Chemistry; Chromatography, Thin Layer; Coenzymes; Culture Media; Hydrogen-Ion Concentration; Kinetics; NAD; NADP; Oxidation-Reduction; Oxidoreductases; Oxygen Consumption; Pseudomonas; Santonin

Topics: Analgesics; Analgesics, Non-Narcotic; Anti-Allergic Agents; Antipyretics; Histamine; Histamine H1 Antagonists; Santonin