A NADPH-dependent reductase activity, capable of converting (+) dihydroquercetin (2,3-trans) to its 3,4-diol (a leucocyanidin), has been demonstrated in crude, soluble protein extracts derived from cell suspension cultures of Douglas fir (Pseudotsuga menziessi). Neither NADH nor ascorbate substituted as the H-donor. Quantitative analyses were based on the production of cyanidin, the formation of an adduct with vanillin, and on absorbance at 280 nanometers. Nonenzymic reduction of (+)-dihydroquercetin with NaBH4 produced two presumably isomeric flavan-3,4,-diols. One of these was similar to the enzymically produced diol, based on products isolated by chromatography on paper, on thin-layer cellulose and on C18 reversed-phase columns (high performance liquid chromatography), and on the conversion of the diol to the all-trans dimer of (+)-catechin upon the addition of (+)-catechin.

Extrats of cel sspnin culturs from Douglas fir (Puado wa minzinji) nedls catalyzed the prductio of (+)-catechin (2,3-tran flavan-3-ol) from the 2,-tras-flavan,3,4-cis-diol (leucocyanidin) in a NADPH-dependent redutas reaction at pH 7A. Catechin was also produced, along with the 3,4-ci-didl, in a double step reductio from (+)-dihydroquercetin. It was necessary to eliminate any thibl such as 2-mercaptoethanol or dithiothreitol from the extract or assay mixture becanse these thiols apparently formed thioethers with the 3,4-diols.

The toxicity of the fungal phytotoxin dothistromin (l) to microorganisms, its lysis of human red blood corpuscles and beetroot tissue, and its unexpectedly selective inhibition of radicle elongation for Trigonella foenum-graecum were strongly light-dependent. Dothistromin was also toxic to Artemia salina but without requiring light activation. It was not active as a wilt or necrosis toxin, possible because of its ready adsorption onto external plant tissue.

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Extracts of callus or cell suspension cultures from petioles of Ginkgo biloba catalyzed the production of (+)-gallocatechin (2,3-trans-3,5,7,3',4',5'-hexahydroxy-flavan) from (+)-dihydromyricetin (5'-hydroxy-dihydroquercetin) along with the expected 3,4-cis-diol intermediate, leucodelphinidin, in a NADPH-dependent double-step reductase reaction at pH 7.4. The latter diol, isolated from the above incubation mixture, produced (+)-gallocatechin in a NADPH-dependent reaction.Extracts from tissue cultures derived from needles of Pseudotsuga menziesii (Douglas fir) also produced significant amounts of the 3,4-diol from dihydromyricetin. (+)-Dihydromyricetin, purified via paper chromatography from leaves of Leptarrhena pyrolifolia, was reduced by NaBH4 to the presumed 3,4-trans-diol and acid epimerized to the 3,4-cis-diol.Two NADPH reductases, acting in sequence to reduce DHQ2 first to its 3,4-cis-diol (leucocyanidin) and then to (+)catechin (diphenolic B-ring), were previously reported in extracts derived from cell suspension cultures of Douglas fir (10, 1 1). A similar set of NADPH-dependent reductases converting DHM to (+)-gallocatechin (triphenolic B-ring) via a 3,4-diol (leucodelphini-