Sempervirenic acid,a diterpene acid from Solidago sempervirens

Sempervirenic acid, a new diterpene has been isolated from Solidago sempervirens and its structure determined by spectroscopic methods and chemical conversions to be 3β-acetoxy-labda-7,13-diene-15-oic acid.     

Rubinic acid,a triterpene acid from rubus fruticosus

A new triterpene acid, rubinic acid, was isolated from the chloroform extract of the leaves of Rubus fruticosus. On the basis of physical methods and chemical degradation experiments, its structure was determined as 7α-hydroxyursonic acid.     

Failure of 3-hydroxy-3-phenylpropanoic acid and cinnamic acid to serve as precursors of tropic acid in Datura innoxia

Datura innoxia plants were fed the R- and S-isomers of [3-¹⁴C]-3-hydroxy-3-phenylpropanoic acid, and [3-¹⁴C]cinnamic acid along with dl-[4-³H]phenylalanine. The hyoscyamine and scopolamine isolated from the plants 7 days later were labeled with tritium, but devoid of ¹⁴C, indicating that 3-hydroxy-3-phenylpropanoic acid and cinnamic acid are not intermediates between phenylalanine and tropic acid. The [³H] tropic acid obtained by hydrolysis of the hyoscyamine was degraded and shown to have essentially all its tritium located at the para position of its phenyl group, a result consistent with previous work.     

Inhibition of α-aminoisobutyric acid uptake by diisothiocyanostilbenedisulphonic acid in the amphibian cornea

α-Aminoisobutyric acid accumulation of the toad's (Bufo marinus) cornea and lens is inhibited by 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid. This effect is seen at pH 8.4; at pH 7.4 a small increase in aminoisobutyric acid uptake was observed. Efflux of aminoisobutyric acid is unchanged by diisothiocyanostilbenedisulphonic acid at either pH. The inhibitory effect of diisothiocyanostilbenedisulphonic acid on aminoisobutyric acid accumulation appears to reflect a direct action on membrane mechanisms that mediate its influx.     

9-Hydroxydodecanoic acid,an acid from Blepharis sindica seed oil

A hitherto unknown hydroxy acid has been isolated from Blepharis sindica seed oil has been characterized as 9-hydroxydodecanoic acid by IR, NMR and mass spectral studies. The structure of this acid was further supported by its chemical transformations.     

Structure of terminic acid,a dihydroxytriterpene carboxylic acid from Terminalia arjuna

The structure of terminic acid, a new dihydroxytriterpene carboxylic acid isolated from the roots of Terminalia arjuna, has been established as 3β, 13β-dihydroxylup-20(29)-en-28-oic acid by a study of its chemical reactions and spectroscopic data. Terminic acid and its derivatives were found to undergo skeletal rearrangement under protonic conditions to yield oleanene lactone.     

A novel abscisic acid metabolite from seeds of Robinia pseudacacia

Abscisic acid and its novel metabolise, which was a conjugated form of hydroxyabscisic acid (Metabolite C), were isolated from seeds of Robinia pseudacacia L. The structure of the conjugate was shown to be (+)-3-methyl-5 - [1(S),6(R) - 2,6 - dimethyl - 1 - hydroxy - 6 - (3 - hydroxy - 3 - methyl - 4 - carboxybutanoyloxymethyl) - 4 - oxo-cyclohex-2-enyl]-2-Z-4-E-pentadienoic acid and tentatively named β-hydroxy-β-methylglutarylhydroxyabscisic acid.     

2-C-Methylaldotetronic acid,a new lactone-forming acid present in plants

2-C-Methylaldotetronic acid (probably the erythro form) was found in considerable amounts in Cannabis sativa, Cereus forbesii, C. peruvianus, Lophophora williamsii, Trichocereus santiaguensis, T. spachianus and T. strigosus. In addition, the acid was present in minor amounts in another five species, all from the Cactaceae. In total, this new plant acid was detected in 12 of 19 investigated species.     

Ascorbalamic acid: An ascorbigen-like plant constituent yielding in hot acid 3-(2-furoyl)alanine

Ascorbalamic acid (C₉H₁₃NO₈) was isolated from Brassica olerocea L. MS study of various methylated derivatives suggested a structure (Ia) derivable by CC coupling of C-3 of alanine with C-2 of ascorbic acid, followed by lactone → lactam rearrangement. Other derivatives provided supporting evidence, as did study of the reaction of L-3-chloroalanine with L-ascorbic acid in vitro. On treatment with hot 6 M HCl, ascorbalamic acid yielded L-aspartic acid and 3-(2-furoyl)alanine. For identification of the latter, DL-3-(2-furoyl)alanine and its N-2,4-dinitrophenyl and N-acetyl methyl ester derivatives were synthesized. Unlike ascorbigens, ascorbalamic acid is probably present in the living plant. It seemed to be present in all crucifers examined, but to have a capricious distribution in other orders. During permethylation, rearrangements of ester groups were observed, both with ascorbalamic acid and with pyrrolidonecarboxylic acid as a model.     

Prelunularic acid in liverworts

Prelunularic acid, the first example of an intermediate with a ‘pre-aromatic’ structure in the phenylpropanoid-polymalonate pathway, was isolated from suspension-cultured cells of Marchantia polymorpha. Its structure, including its absolute configuration, was assigned on the basis of spectral properties, direct conversion into lunularic acid, and CD measurements on the bis(p-dimethylaminobenzoate) of the methyl ester. Prelunularic acid was also detected in several liverworts of Marchantiales and Jungermanniales, and appears to be the immediate precursor of lunularic acid instead of the previously postulated hydrangenol or hydrangeic acid.     

Occurrence,structure and synthesis of 3-(N-Methylamino)glutaric acid,an amino acid from Prochloron didemnii

3-(N-Methylamino)glutaric acid has been identified as a new free amino acid in extracts from Prochloron didemnii (Lewin), a unique prokaryotic algal symbiont associated with certain didemnid ascidians. Its structure was established by elucidation of the mass spectra of its TMSi and other derivatives and confirmed by synthesis.     

GC-MS identification of abscisic acid and abscisic acid metabolites in seed of Vigna unguiculata

Abscisic acid, phaseic acid and 4′-dihydrophaseic acid were identified by GC-MS of derivatized (Me, MeTMSi) extracts from immature fruits of Vigna unguiculata. The fruits also contained some other ABA-related compounds, one of which might be epi-4′-dihydrophaseic acid while another was tentatively identified as 6′-hydroxymethylabscisic acid.     

Adaptive evolution improves acid tolerance and succinic acid production in Actinobacillus succinogenes

Fermentation at low pH is an efficient way to improve the competitiveness of biological succinic acid-producing process. Actinobacillus succinogenes shows good performance of succinic acid production under anaerobic conditions, but its succinic acid production capability at the low-pH is inefficient due to the poor acid resistance. Herein, a mutant A. succinogenes BC-4 with improved cell growth and succinic acid production under weak acid conditions was obtained by adaptive evolution. The specific growth rate and succinic acid production of BC-4 reached 0.13 g/L/h and 20.77 g/L, which were increased by 3.25- and 2.95- fold, respectively compared with the parent strain under anaerobic condition at pH 5.8. The activities of specific enzymes with ATP generation were significantly enhanced under weak acidic conditions, resulting in 1.28-fold increase in the maximum ATP level. Membrane fatty acid composition analysis demonstrated that the ratio of saturated to unsaturated fatty acids was decreased from 1.62 to 1.44 in mutant BC-4, leading to improved intracellular pH homeostasis. Furthermore, the change from long-chain to median-chain fatty acid might lower the permeability of H⁺ into cytoplasm for survival under acid stress. These results indicated that A. succinogenes BC-4 is a promising candidate for succinic acid production under weak acid condition.     

Lactic acid bacteria isolated from fish gut produce conjugated linoleic acid without the addition of exogenous substrate

The production of conjugated linoleic acid (CLA) by four strains of lactic acid bacteria isolated from fish, i.e., Leuconostoc mesenteroides H20, Leuconostoc mesenteroides H22, Leuconostoc lactis H24 and Lactobacillus pentosus H16, was evaluated in MRS broth and on MRS agar. The bioconversion and production of CLA by resting cells were also assessed. Linoleic acid was detected in cultures grown on agar at percentages of up to 18.3% (w/w) of total fatty acid, and conjugated isomers were found in the fatty acid profiles of Lactobacillus pentosus H16. The percentage of CLA relative to total fatty acid increased from 5.68 ± 1.65% to 23.69 ± 0.79% when resting cells were removed from agar plates and incubated without the addition of exogenous linoleic acid as a substrate. When Lactobacillus pentosus H16 cells were incubated with linoleic acid, cyclization and changes in monounsaturated fatty acid percentages were observed instead of conjugation. These results show that growth on a solid support is required for CLA production. More significantly, an increase in the CLA content could be achieved by incubating resting cells without exogenous substrate.     

Isolimonic acid,a new citrus limonoid

Isolimonic acid was isolated as its methyl ester from seeds of Citrus aurantium, C. reticulata and C. paradisi, and its structure was determined by ¹H and ¹³C NMR. The isomeric limonoid ichangin was also isolated from C. aurantium and C. paradisi.     

An inducible lactone hydrolase yielding 2,5-diphenyl-3-hydroxy-4-oxo-2-hexendioic acid from pulvinic acid

The metabolism of vulpinic acid by an unclassified soil micro-organism was studied. A new compound, 2,5-diphenyl-3-hydroxy-4-oxo-2-hexendioic acid (DHOHA) was isolated from the reaction mixture of a cell-free preparation and pulvinic acid. The existence of a hydrolase which catalyses the conversion of vulpinic acid to pulvinic acid was detected in cell-free preparation, and an inducible lactone hydrolase capable of converting pulvinic acid to DHOHA was purified 130-fold and characterized. This enzyme had a MW of ca 34 000, a K_m for pulvinic acid at pH optimum (pH 7.0) less than 10 ^{? 6} M, pI = 5.0, and was inhibited by p-chloromercuriphenylsulfonate and diethylpyrocarbonate. The enzyme was highly specific for pulvinic acid. The initial degradative steps proposed for this organism are vulpinic acid → pulvinic acid → DHOHA.     

Heterologous production of caffeic acid from tyrosine in Escherichia coli

Caffeic acid is a plant secondary metabolite and its biological synthesis has attracted increased attention due to its beneficial effects on human health. In this study, Escherichia coli was engineered for the production of caffeic acid using tyrosine as the initial precursor of the pathway. The pathway design included tyrosine ammonia lyase (TAL) from Rhodotorula glutinis to convert tyrosine to p-coumaric acid and 4-coumarate 3-hydroxylase (C3H) from Saccharothrix espanaensis or cytochrome P450 CYP199A2 from Rhodopseudomonas palustris to convert p-coumaric acid to caffeic acid. The genes were codon-optimized and different combinations of plasmids were used to improve the titer of caffeic acid. TAL was able to efficiently convert 3 mM of tyrosine to p-coumaric acid with the highest production obtained being 2.62 mM (472 mg/L). CYP199A2 exhibited higher catalytic activity towards p-coumaric acid than C3H. The highest caffeic acid production obtained using TAL and CYP199A2 and TAL and C3H was 1.56 mM (280 mg/L) and 1 mM (180 mg/L), respectively. This is the first study that shows caffeic acid production using CYP199A2 and tyrosine as the initial precursor. This study suggests the possibility of further producing more complex plant secondary metabolites like flavonoids and curcuminoids.     

Vergatic acid,a new pentacyclic triterpene from Salvia virgata

A new pentacyclic triterpene acid was isolated from the arial parts of Salvia virgata and its constitution was established as 3β-hydroxy-1-oxo-olean-12-en-28-oic acid and named virgatic acid.     

A new diterpenic acid and other constituents of Haplopappus foliosus and H. Angustifolius

Hentriacontane, friedelan-3-one, epi-friedelinol, hexacosanol, stigmasterol, a new diterpenic acid and its monomethyl ester are amongst the constituents of Haplopappus foliosus and H. angustifoliosus. The new acid has been called haplopappic acid.