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At least 19 recordsLinked to original sources
PubMed2026

Biochemical analysis of the TPS-b subfamily reveals a cineole-centered monoterpene biosynthetic module in Medicago truncatula.

Terpenoids constitute one of the largest and most structurally diverse classes of plant specialized metabolites, with diversity generated by terpene synthases (TPSs) and downstream tailoring enzymes. In Medicago truncatula, the TPS-b subfamily comprises five putative synthases, two of which are embedded within a previously uncharacterized genomic locus containing a cytochrome P450 (CYP) and a BAHD-type acyltransferase. Here, we present a comprehensive biochemical analysis of the M. truncatula TPS-b subfamily and define a cineole-centered monoterpene biosynthetic module. Heterologous expression and in vitro assays with multiple prenyl diphosphate substrates revealed three catalytically active TPS-b enzymes with distinct substrate preferences and product profiles. MtTPS4 functions as a dedicated (E)-β-ocimene synthase, whereas MtTPS15 exhibits substrate-dependent bifunctionality, producing (E)-β-ocimene from geranyl diphosphate and α-farnesene from farnesyl diphosphate. MtTPS36 generates 1,8-cineole as the predominant product alongside α-terpineol from geranyl and neryl diphosphate. Genome analysis revealed that MtTPS36 is colocalized with a cytochrome P450 belonging to the CYP736 family. Biochemical characterization of this CYP identified a previously undescribed plant cineole hydroxylase that catalyzes oxidation of 1,8-cineole to yield 2α-hydroxy-1,8-cineole (also known as 2-exo-hydroxy-1,8-cineole), establishing a TPS-CYP biosynthetic module. These results define the gene-to-metabolite relationships within the TPS-b subfamily in M. truncatula and expand the known enzymatic biosynthetic capacity underlying oxygenated monoterpene biosynthesis in plants.

1,8-Cineole↗
PubMed1978

The effect of dietary monoterpenes on the cholesterol level of eggs.

Monoterpenes were included in the diets of laying hens in an attempt to inhibit the synthesis of cholesterol and hence reduce its amount in egg yolk. However, feeding five monoterpenes, phorone or 200 mg. cholesterol per day to hens did not significantly change the level of cholesterol in the egg yolk. These compounds did not cause signs of ill health in the hen or a decline in egg production.

Animals↗
PubMed1976

Characterization of a cytochrome P-450 dependent monoterpene hydroxylase from the higher plant Vinca rosea.

A monooxygenase isolated from 5-day old etiolated Vinca rosea seedlings was shown to catalyze the hydroxylation of the monoterpene alcohols, geraniol and nerol, to their corresponding 10-hydroxy derivatives. Hydroxylase activity was inpendent upon NADPH (neither NADH nor combination of NADH, NADP+ and ATP served as substitutes) and O2. Geraniol hydroxylation was enhanced by dithiothreitol (monothiols were less effective) and inhibited by phospholipases, thiol reagents, metyrapone, and cytochrome c, as well as other inhibitors of cytochrome P-450 systems. Geraniol was hydroxylated at a faster rate than nerol, but the alcohols possessed similar apparent Km values. The membrane-bound hydroxylase was solubilized by treatment with sodium cholate, Renex-30, or Lubrol-WX. Cholate-treated enzyme was resolved by DEAE-cellulose chromatography and reconstitution of the hydroxylase was effected utilizing different fractions containing cytochrome P-450, a NADPH-cytochrome c reductase, and lipid.

Binding Sites↗
PubMed1979

Selective oocyte degeneration and impaired fertility in rats treated with the aliphatic monoterpene, Citral.

Mature female rats treated with Citral (3-7-dimethyl-2,6-octadienal) either topically for 60 or 100 days or by 6 i.p. injections (at 4-5 day day intervals) showed a marked decrease in the number of normal follicles per section, because oocytes tended to degenerate although the follicular cells remained normal. The reproductive performance after Citral treatment was impaired: there was a reduction in implantation number and litter size and an increased post-implantation fetal wastage. None of the young survived after 100 days of topical Citral treatment. It is suggested that Citral directly affects the oocytes.

Acyclic Monoterpenes↗
PubMedDate not supplied

Behavioral and toxicological studies of cyclopentanoid monoterpenes from Nepeta cataria.

Two samples of catnip oil were analyzed by tic, gc, and hplc; the results indicated the presence of 23 components. Fractionation of the commercial sample of catnip oil by either distillation or gc yielded 40% nepetalactone and 43% nepetalic acid. Catnip oil, nepetalic acid, and a nepetalactone-enriched fraction were evaluated for toxicological and behavioral effects in mice and rats. The LD50 of catnip oil, the nepetalactone-enriched fraction, and nepetalic acid were found in mice to be: 1300 mg/kg, 1550 mg/kg and 1050 mg/kg, respectively. Catnip oil (500 mg/kg) and nepetalic acid (62.5 mg/kg) were found to significantly increase hexobarbital sleeping time in mice. Rats trained on a Sidman avoidance schedule showed a significant decrease in performance following intraperitoneal injections of catnip oil (500--750 mg/kg), nepetalic acid (125--250 mg/kg), and the nepetalactone-enriched fraction (500--750 mg/kg). Rats trained on the same avoidance schedule developed behavioral tolerance after daily injections of 750 mg/kg catnip oil.

Animals↗
PubMed2026

Eucalyptol mitigates isoproterenol-induced myocardial injury in rats via activation of p38 MAPK/JNK signaling, suppression of ER stress, and modulation of apoptotic pathway.

BACKGROUND: Myocardial injury (MI), a subset of cardiovascular diseases, remains a leading cause of deaths globally, driven by pathological inflammation, oxidative stress, and apoptosis. Despite advances in interventional cardiology, high relapse rates and therapeutic limitations underscore the urgent need for novel pharmacological agents. Phytochemicals, with their multi-target approach and favorable safety profiles, offer promising alternatives for mitigating ischemic injury. METHODS: The cardioprotective effects of 1,8-cineole, a monoterpene derived from Eucalyptus species, was investigated in a rat model of isoproterenol-induced myocardial injury. Serum levels of cardiac enzymes (creatine kinase (CK), lactate dehydrogenase (LDH)) and pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) were quantified. Preliminary histopathological analysis was performed to assess the extent of myocardial damage. Key molecular mechanisms were evaluated via western blotting and immunohistochemistry, examining pathways related to inflammation (NF-κB), apoptosis (Bcl-2/Bax, caspase-3), endoplasmic reticulum (ER) stress (GRP78, CHOP, PERK-eIF2α), and antioxidant defense (GSH, SOD, CAT). RESULTS: Our results demonstrate that 1,8-cineole significantly reduced the levels of serum cardiac enzymes (CK-MB, LDH), and histopathological damage. Mechanistically, 1,8-cineole also suppressed pro-inflammatory cytokine release (TNF-α, IL-6, and IL-1β) via inhibition of the NF-κB pathway. Furthermore, it attenuated cardiomyocyte apoptosis by modulating Bcl-2/Bax expression and inhibiting caspase-3 activation. Additionally, 1,8-cineole alleviated ER stress by downregulating GRP78, CHOP, and PERK-eIF2α signaling. Importantly, we identified enhanced Nrf2 nuclear translocation and subsequent upregulation of antioxidant enzymes (GSH, SOD, CAT) as key contributors to its cytoprotective effects. CONCLUSIONS: 1,8-Cineole exhibits potent cardio-protection in experimental myocardial injury by targetinginflammation, apoptosis, ER stress, and oxidative stress through modulation of p38 MAPK/JNK, suppression of inflammatory markers (TNF-α, IL-6, IL-1β) and apoptotic markers (Bax, p53). Its natural origin, bioavailability, and multi-mechanistic effectiveness make it a promising candidate for translational development as an adjunct therapy for myocardial injury.

Animals↗
PubMed2025

Integrated genomic, transcriptomic, and metabolomic analyses of Chrysanthemum aromaticum provide insights into the volatile terpene biosynthesis.

Chrysanthemum aromaticum is renowned for its uniformly emitted strong and attractive scent, primarily attributed to volatile terpenes. Despite its commercial and horticultural significance, the molecular mechanisms underlying volatile terpene production in C. aromaticum remain largely unexplored. Here, we present the haplotype-resolved genome assembly of C. aromaticum, with a total size of 3.10 Gb, comprising nine anchored chromosomes with a contig N50 of 30.66 Mb and a scaffold N50 of 350.58 Mb. Phylogenetic analyses revealed a distant relationship between C. aromaticum and C. indicum, suggesting that C. aromaticum likely represents a distinct species rather than a variety of C. indicum. Through integrated genomic, transcriptomic, metabolomic, and biochemical analyses, we identified seven TPS involved in monoterpene biosynthesis and six TPS for sesquiterpene biosynthesis. Notably, comparative genomic analysis revealed a gene cluster for α-bisabolol biosynthesis in C. aromaticum, which has specifically expanded in Chrysanthemum species through tandem gene duplications, contributing to the elevated accumulation of α-bisabolol in the leaves of C. aromaticum. Our study provides important insights into the biosynthesis of volatile terpenes, highlighting the genetic basis for C. aromaticum's unique aromatic profile.

Chrysanthemum↗
PubMed1977

Binding specificity of the juvenile hormone carrier protein from the hemolymph of the tobacco hornworm Manduca sexta Johannson (Lepidoptera: Sphingidae).

A series of analogues of insect juvenile hormone (four geometric isomers of methyl epoxyfarnesenate, several para-substituted epoxygeranyl phenyl ethers, and epoxyfarnesol and its acetate and haloacetate derivatives) was prepared to investigate the binding specificity of the hemolymph juvenile hormone binding protein from the tobacco hornworm Manduct sexta. The relative binding affinities were determined by a competition assay against radiolabeled methyl (E,E)-3,11-dimethyl-7-ethyl-cis-10,11-epoxytrideca-2,6-dienoate (JH I). The ratio of dissociation constants was estimated by plotting competitor data according to a linear transformation of the dissociation equations describing competition of two ligands for a binding protein. The importance of the geometry of the sesquiterpene hydrocarbon chain is indicated by the fact that the binding affinity is decreased as Z (cis) double bonds are substituted for E (trans) double bonds in the methyl epoxyfarnesenate series; the unepoxidized analogues do not bind. A carboxylic ester function is important although its orientation can be reversed, as indicated by the good binding of epoxyfarnesyl acetate. In the monoterpene series, methyl epoxygeranoate shows no affinity for the binding protein, but substitution of a phenyl or p-carbomethoxyphenyl ether for the ester function imparts a low, but significant affinity. These data taken together with earlier results indicate that the binding site for juvenile hormone in the hemolymph binding protein is characterized by a sterically defined hydrophobic region with polar sites that recognize the epoxide and the ester functions.

Animals↗
PubMed1976

Multiple acyl-coenzyme A carboxylases in Pseudomonas citronellolis.

Pseudomonas citronellolis was shown to contain four different acyl-coenzyme A carboxylases, including acetyl-, propionyl-, 3-methylcrotonyl-, and geranyl-CoA carboxylases, when grown on the appropriate carbon sources. Acetyl-CoA carboxylase activity in crude extracts was stimulated approximately 40-fold by inclusion of 0.4-0.5 M ammonium sulfate in the assay. Unexpectedly high levels of propionyl-CoA carboxylase activity, also stimulated by ammonium sulfate, were found in acetate-grown cells. That these acetyl- and propionyl-CoA carboxylase activities were due to different enzymes was shown by their resolution during purification by a procedure that stabilized acetyl-CoA carboxylase as a complex and separated propionyl-CoA carboxylase into two required protein fractions. Propionate- or valine-grown cells contained a propionyl-CoA carboxylase activity that was strongly inhibited by ammonium sulfate in the assay, and which may represent an inducible form of the enzyme. Geranyl- and 3-methylcrotonyl-CoA carboxylases that catalyze the carboxylation of the 3-methyl groups of homologous acyl-CoA acceptors, were induced by growth on the monoterpenes, citronellic or geranoic acid; only 3-methylcrotonyl-CoA carboxylase was induced by growth on leucine or isovaleric acid. Induction of either carboxylase was associated with the appearance of similar high-molecular-weight, biotin-containing proteins as measured by gel filtration. These two carboxylases are probably distinct enzymes since 3-methyl-crotonyl-CoA carboxylase from isovalerate-grown cells does not carboxylate geranyl-CoA, while geranyl-CoA carboxylase will carboxylate both acyl-CoA homologues. P. citronellolis appears to be a useful system for studying the structural aspects of pairs of homologous acyl-CoA carboxylases.

Acetyl-CoA Carboxylase↗
PubMed2026

Divergent Lineage of Terpene Synthases Establishes Terpenoid Biosynthesis in Brown Macroalgae.

Brown algae of the order Dictyotales uniquely stand out among stramenopiles (heterokonts) as prolific producers of bioactive terpenoid molecules associated with chemical defense and antifouling. Although more than 200 sesquiterpenoids and diterpenoids have been reported, largely from the genera of Dictyota and Dictyopteris, their biosynthetic origin has remained unknown for decades. Leveraging de novo genome and transcriptome sequencing in the nonmodel alga Dictyota coriacea, we identified a brown algal-specific lineage of type I terpene synthases (TSs) that harbors novel catalytic motifs distinct from those characterized in plants, microbes, red algae, and metazoans. Across three brown algal species, we characterized 15 terpene synthases, including DcTS-2, which produces the diterpene alcohol dilophol, a proposed biosynthetic intermediate to the antifouling metabolite pachydictyol A. X-ray crystal structures of the monoterpene synthase DcTS-3 further revealed that the brown algal enzymes retain the canonical terpene synthase fold, and together with mutagenesis studies, suggest the catalytic role of the novel motifs defining this newly established evolutionary lineage. Brown algal terpene synthases separate into two subgroups, with mono- and diTSs containing putative chloroplast-targeting sequences while sesquiTSs lack them, suggesting convergent compartmentalization of terpene biosynthesis with land plants. Together, these findings establish the molecular basis of terpenoid biosynthesis in brown algae and highlight the challenges of adapting established biosynthetic logic to nonmodel marine algae.

Alkyl and Aryl Transferases↗