Neolignans from an Aniba species

A benzene extract of the trunk wood of an Aniba species contained 3a-allyl-2-aryl-5-methoxy-3-methyl-2,3,3a,6-tetrahydro-6-oxobenzofurans which may be responsible, through sequential Cope, retro-Claisen and Claisen rearrangements respectively for the formation of the co-occurring 5-allyl-2-aryl-5-methoxy-3-methyl-2,3,5,6-tetrahydro-6-oxobenzofurans; the 6-O-allyl-2-aryl-5-methoxy-3-methyl-2,3-dihydrobenzofurans and the 7-allyl-2-aryl-6-hydroxy-5-methoxy-3-methyl-2,3-dihydrobenzofurans. The examination of the stereochemistry of these products led to the formulation of burchellin, previously isolated from Aniba burchellii Kostermans, as (2S,3S,3aR)-3a-allyl-5-methoxy-2-piperonyl-3-methyl-2,3,3a,6-tetrahydro-6-oxobenzofuran. The structure 1-allyl-4,8-dihydroxy-7-(3-methoxy-4,5-methylenedioxyphenyl)-6-methyl-3-oxobicyclo[3,2,1]octane is tentatively proposed for an additional neolignan.     

Membrane-associated reactions in ubiquinone biosynthesis: 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone methyltransferase

The O-methylation of 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone, which has been previously postulated to be the final reaction in the biosynthesis of ubiquinone was demonstrated in vitro using cell extracts of Escherichia coli. $\text{S-}\text{Adenosyl}\text{-}\text{l}\text{-}\text{methionine}$ was active as the methyl donor for the reaction. The enzyme concerned, S-adenosyl-l-methionine: 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone-O- methyltransferase, was partially purified and shown to have a molecular weight of about 50 000 and to require a divalent metal and dithiothreitol for optimal acitivity in vitro. The methyltransferase was absent from extracts from ubiG^? mutants suggesting that the ubiG gene is the structural gene coding for the methyltransferase. The enzyme, although not firmly membrane-bound, showed some affinity for the cell membrane in broken cell preparations and could utilize the benzoquinone substrate when the latter was free or bound to the cell membrane, with about equal efficiency. It is concluded that in vivo, the methyltransferase reaction probably occurs at the internal surface of the cytoplasmic membrane.     

New isoflavonoid glycosides from Dalbergia paniculata

The methanolic extract of the bark of Dalbergia paniculata has yielded three new isoflavonoid glycosides whose structures have been determined. They are 8-C-glucosylprunetin and biochanin-A and formononetin 7-rutinosides.     

A new dihydrobenzofuran from Liatris provincialis

A chloroform extract of Liatris provincialis Godfrey gave as a minor component a new dihydrobenzofuran, whose structure was established as I.     

Aerobic respiration in mutants of Escherichia coli accumulating quinone analogues of ubiquinone

The ability of three naturally occurring analogues of ubiquinone to function in aerobic respiration in Escherichia coli has been studied. The compounds, which differ from ubiquinone in terms of the substituents on the quinone ring, accumulate in the cytoplasmic membranes of ubiE^?, ubiF^? and ubiG^? mutants. One of the analogues (2-octaprenyl-3-methyl-6-methoxy-1,4-benzoquinone, MMQ), which lacks the 5-methoxyl group of the benzoquinone ring of ubiquinone promoted the oxidation of NADH, d-lactate and α-glycerophosphate but not succinate. Electron transport supported by MMQ was found to be coupled to phosphorylation. In contrast, 2-octaprenyl-6-methoxy-1,4-benzoquinone, which lacks both the 3-methyl and 5-methoxyl groups of ubiquinone, and 2-octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinone, in which the 5-methoxyl group of ubiquinone is replaced by an hydroxyl group, were virtually inactive in the oxidases tested. The ability of MMQ to function in respiration in isolated membranes is consistent with the findings that the growth rate and yield of a ubiF^? strain, unlike other ubi^? strains, were only slightly lower than those of a ubiF⁺ strain.The fact that MMQ is active in some but not all oxidases provides further support for the concept that the quinones link the individual dehydrogenases to the respiratory chain and that each dehydrogenase has specific structural requirements for quinone acceptors.     

Volubilin,a new isoflavone-C-glycoside from Dalbergia volubilis flowers

Dalbergia volubilis flowers after successive extraction with light petroleum, benzene and alcohol yielded β-sitosterol, stigmasterol, biochanin-A and a new isoflavone-C-glycoside named volubilin. The glvcoside on boiling with HI and phenol gave genistein and on ferric chloride oxidation rhamnose. The compound was identified as 8-C-rhamnopyranosyl-genistein-4′,7-dimethyl ether by means of chemical reactions as well as from spectral data.     

Isoflavanoid constituents from Dalbergia monetaria

The structures and isolation of eight compounds from Dalbergia monetaria seeds are described. Four of them are known rotenoids. In addition to a new isoflavone and its 7-β-D-glucoside, the first 12-dihydrorotenone, 12-dihydrodalbinol, and its 8′-β-D-glucoside were identified.     

Porosin: A neolignan from Ocotea porosa

The wood of Ocotea porosa (Nees) L. Barr. (Lauraceae) contains sitosterol, sesquiterpenes, n-octacosanoic acid, n-hexacosanoic acid and the neolignan porosin for which the structure of 3a-allyl-5-methoxy-3-methyl-2-veratryl-2,3,3a,6,7,7a-hexahydro-6-oxobenzofuran (II) is proposed.     

Neoflavanoids of Dalbergia cultrata

In addition to the known neoflavanoids (S)-4-methoxydalbergione, dalbergin, and stevenin, the heartwood of Dalbergia cultrata Grah. contains a new 3,3-diphenylprop-l-ene (Ia). The assigned structure is based on data acquired mainly by physical methods. The softwood of D. ferruginea Roxb. ¹ yielded sitosterol and friedelin.     

Diterpenoids from Caesalpinia pulcherrima

Three new furanoditerpenoids of the caesalpin-type have been isolated from the roots of Caesalpinia pulcherrima. The structures of these compounds, vouacapen-5α-ol, 6β-cinnamoyl-7β-hydroxy-vouacapen-5α-ol and 8,9,11,14-didehydrovouacapen-5α-ol, were elucidated through interpretation of their spectral data. Sitosterol was also obtained.     

Flavonoid and ceroptin pigments from frond exudates of Pityrogramma triangularis

Two chemically distinct golden-yellow flavonoid exudates occur on the underside of fronds of Pityrogramma triangularis: ceroptin and a newly described flavonol, 6-methyl-8-methoxy-3,5,7-trihydroxyflavone were detected in one of the exudates and two methylated kaempferol derivatives, 4′-methoxy-3,5,7-trihydroxyflavone and 3,5-dihydroxy-7,4′-dimethoxyflavone were isolated from the other.