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.     

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.     

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.     

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.     

Plectranthoic acid,acetylplectranthoic acid and plectranthadiol,three triterpenoids from Plectranthus rugosus

Sitosterol and three new pentacyclic triterpenoids, plectranthoic acid, acetylplectranthoic acid and plectranthadiol, have been isolated from leaves of P. rugosus. From spectroscopic evidence and chemical behaviour the structure of plectranthoic acid was established as (19S)-3α-hydroxy-18α-urs-12-en-29β-oic acid and acetylplectranthoic acid is the 3α-acetyl derivative of this compound. Plectranthadiol is (19S)- 3α-hydroxy-18α-urs-12-en-29β-ol.     

Gallic acid oxidation by turnip peroxidase

Both ellagic and gallic acids non competitively inhibited guaiacol oxidation by turnip peroxidase. The K_i values were 3 and 26 μm for ellagic and gallic acid respectively. Enzymatic oxidation of gallic acid by the isolated major turnip peroxidase was characterized with respect to spectral behaviour, affinity constant and pH effect. The K_m for H₂O₂ and gallic acid are 2.5 and 8.0 mM for turnip peroxidase. The pH optimum for gallic acid oxidation is about 6.5 and the rate constant k₄ decreased with the increase of pH in presence of both guaiacol and Gallic acid. When the gallic acid oxidation products were subjected to chromatographic analysis, it was found to be converted mainly to ellagic and an unknown quinone.     

Anhydrobartogenic acid and 19-epibartogenic acid,two triterpenes from Barringtonia speciosa

Two new triterpene dicarboxylic acids, isolated from the fruits of Barringtonia speciosa, have been identified as anhydrobartogenic acid and 19-epibartogenic acid by spectral and chemical evidence.     

Structure-activity relationships of trans-substituted-propenoic acid derivatives on the nicotinic acid receptor HCA2 (GPR109A)

Nicotinic acid (niacin) has been used for decades as an antidyslipidemic drug in man. Its main target is the hydroxy-carboxylic acid receptor HCA2 (GPR109A), a G protein-coupled receptor. Other acids and esters such as methyl fumarate also interact with the receptor, which constituted the basis for the current study. We synthesized a novel series of substituted propenoic acids, such as fumaric acid esters, fumaric acid amides and cinnamic acid derivatives, and determined their affinities for the HCA2 receptor. We observed a rather restricted binding pocket on the receptor with trans-cinnamic acid being the largest planar ligand in our series with appreciable affinity for the receptor. Molecular modeling and analysis of the structure-activity relationships in the series suggest a planar trans-propenoic acid pharmacophore with a maximum length of 8 Å and out-of-plane orientation of the larger substituents.     

Metabolic engineering of Clostridium acetobutylicum for butyric acid production with high butyric acid selectivity

A typical characteristic of the butyric acid-producing Clostridium is coproduction of both butyric and acetic acids. Increasing the butyric acid selectivity important for economical butyric acid production has been rather difficult in clostridia due to their complex metabolic pathways. In this work, Clostridium acetobutylicum was metabolically engineered for highly selective butyric acid production. For this purpose, the second butyrate kinase of C. acetobutylicum encoded by the bukII gene instead of butyrate kinase I encoded by the buk gene was employed. Furthermore, metabolic pathways were engineered to further enhance the NADH-driving force. Batch fermentation of the metabolically engineered C. acetobutylicum strain HCBEKW (pta⁻, buk⁻, ctfB⁻ and adhE1⁻) at pH 6.0 resulted in the production of 32.5 g/L of butyric acid with a butyric-to-acetic acid ratio (BA/AA ratio) of 31.3 g/g from 83.3 g/L of glucose. By further knocking out the hydA gene (encoding hydrogenase) in the HCBEKW strain, the butyric acid titer was not further improved in batch fermentation. However, the BA/AA ratio (28.5 g/g) obtained with the HYCBEKW strain (pta⁻, buk⁻, ctfB⁻, adhE1⁻ and hydA⁻) was 1.6 times higher than that (18.2 g/g) obtained with the HCBEKW strain at pH 5.0, while no improvement was observed at pH 6.0. These results suggested that the buk gene knockout was essential to get a high butyric acid selectivity to acetic acid in C. acetobutylicum.     

Jessic acid and related acid triterpenoids from combretum elaeagnoides

A novel triterpenoid acid, jessic acid, was extracted from the leaves of Combretum elaeagnoides, where it was found together with its methyl ester and its α-L-arabinopyranoside, all three compounds occurring in significantly large amounts. Jessic acid is 1α,3β-dihydroxy-23-oxo-24-methylenecycloartan-30-oic acid.     

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.     

2-amino-4-acetylaminobutyric acid, 2,4-diaminobutyric acid and 2-amino-6N-oxalylureidopropionic acid (oxalylalbizziine) in seeds of acacia angustissima

A new amino acid previously detected in 17 species of Acacia has been isolated from seeds of Acacia angustissima and identified as oxalylalbizziine. These seeds also contain more than 6% dry weight of 2-amino-4-acetylaminobutyric acid, which has not been reported previously in a legume, and lower concentrations of 2,4-diaminobutyric 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.     

Origin of cyclohexanecarboxylic acid in Bacillus acidocaldarius

In Bacillus acidocaldarius, shikimic acid is converted into the cyclohexancearboxylic acid precursor of fatty acids by way of cyclohexene-l-carboxylic acid, but not by way of cyclohexene-3- or -4-carboxylic acid or benzoic acid.     

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.     

Biosynthetic conversion of α-methylbutyric acid to tiglic acid in Datura meteloides

The administration of RS-α-methylbutyric-[1-¹⁴C] acid to Datura meteloides plants resulted in the formation of radioactive meteloidine. A systematic degradation indicated that essentially all the activity was located at C-1 of the tiglic acid moiety of the alkaloid.     

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.     

Metabolism of abscisic acid and the occurrence of epi-dihydrophaseic acid in Phaseolus vulgaris

When (±)-abscisic acid-[2-¹⁴C] or (±)-abscisic acid-[4′-¹⁸O] was fed to bean (Phaseolus vulgaris) shoots, phaseic acid (PA) and dihydrophaseic acid (DPA) were the major metabolites, while epi-dihydrophaseic acid (epi-DPA) appeared as a minor metabolite. In the acidic fraction the amount of epi-DPA ranged from 18 to 42% of the DPA content, in the conjugated form from 50 to 200%. The content of endogenous epi-DPA amounted to only 1–2% of that of the DPA. These data indicate that the applied abscisic acid is not metabolised in a manner identical with that of the endogenous material. DPA and epi-DPA were shown to be formed separately from PA and could not be inter-converted either by the extraction conditions employed or when fed to bean shoots during short term experiments.     

Cis-4-hydroxypipecolic acid and 2,4-cis-4,5-trans-4,5-dihydroxypipecolic acid from Calliandra

cis-4-Hydroxypipecolic acid and 2,4-cis-4,5-trans-4,5-dihydroxypipecolic acid were isolated from leaves of Calliandra pittieri. A system for resolving the eight imino acids isolated from Calliandra is described.