Synthesis of Sulfur-Containing Analogues of Hedychenone, a Labdane Diterpenoid from Hedychium spicatum

A new iridoid from the roots of Valeriana jatamansi Jones with α-glucosidase activity

One new iridoid namely rupesin F (1) together with four known ones (2-5) were isolated from the roots of Valeriana jatamansi Jones. The structures were established using spectroscopic methods (1D and 2D NMR including HSQC, HMBC, COSY and NOESY) and by comparison with previously published literature data. The isolated compounds 1 and 3 exhibited strong α-glucosidase inhibition activity with IC50 values of 10.13 ± 0.11 and 9.13 ± 0.03 μg/mL, respectively. This study enriched the chemical diversity of metabolites and provides a direction for the development of antidiabetic agents.

Isocratic elution based analytical method for quantification of phytoconstituents in Hedychium spicatum and evaluation of their α-glucosidase inhibitory activity

An efficient, fast, selective and simple isocratic elution method has been established using ultra performance liquid chromatography coupled to photodiode array detection and electrospray ionisation mass spectrometry (UPLC-PDA-ESI-MS) techniques for the quantification of isolated molecules from Hedychium spicatum rhizomes and assess their α-glucosidase inhibitory activity. Developed analytical method was validated as per the regulatory guidelines such as linearity, selectivity, the limits of detection (LOD) and quantification (LOQ), repeatability and accuracy. Highest concentration of 7-hydroxy hedychenone (4) (76.7 mg/g of dried plant material) was detected in rhizomes. Present results demonstrated parent extract (ethanolic) had the greatest inhibitory effect on α-glucosidase with IC50 values of 4.0 µg/mL. Developed method can be used as a new analytical approach for quality assessment of H. spicatum based herbal formulations and other products. Furthermore, current findings showed that the extract, fraction and isolated metabolites may be a good natural antidiabetic.

Extending the Structural Diversity of Labdane Diterpenoids from Marine-Derived Fungus Talaromyces sp. HDN151403 Using Heterologous Expression

Heterologous biosynthesis has become an effective means to activate fungal silent biosynthetic gene clusters (BGCs) and efficiently utilize fungal genetic resources. Herein, thirteen labdane diterpene derivatives, including five undescribed ones named talarobicins A-E (3-7), were discovered via heterologous expression of a silent BGC (labd) in Aspergillus nidulans. Their structures with absolute configurations were elucidated using extensive MS and NMR spectroscopic methods, as well as electronic circular dichroism (ECD) calculations. These labdanes belong to four skeleton types, and talarobicin B (4) is the first 3,18-dinor-2,3:4,18-diseco-labdane diterpene with the cleavage of the C2-C3 bond in ring A and the decarboxylation at C-3 and C-18. Talarobicin B (4) represents the key intermediate in the biosynthesis of penioxalicin and compound 13. The combinatorial heterologous expression and feeding experiments revealed that the cytochrome P450 enzymes LabdC, LabdE, and LabdF were responsible for catalyzing various chemical reactions, such as oxidation, decarboxylation, and methylation. All of the compounds are noncytotoxic, and compounds 2 and 8 displayed inhibitory effects against methicillin-resistant coagulase-negative staphylococci (MRCNS) and Bacillus cereus.

Chemodiversity and α-Glucosidase Activity of Eucalyptus Species from Northwestern Himalaya, India

The aim of current work was to determine essential oils (EOs) composition from three Eucalyptus species, including E. citriodora, E. camaldulensis and E. globulus and assess their α-glucosidase inhibitory activity. The EOs were collected using the hydrodistillation technique and characterized by GC/MS, GC-FID and NMR. The isolated EOs from leaves parts of Eucalyptus species varied from 0.56 to 1.0 % on fresh weight basis. The content of the EOs was distinct according to the species. The most abundant metabolites were identified as citronellal (0-83.0 %), 1,8-cineole (0.2-44.8 %), spathulenol (0.4-16.1 %) α-pinene (0.4-15.9 %), p-cymene (3.7-11.9 %), citronellol (0-8.6 %), β-eudesmol (5.3-8.6 %) and β-pinene (0-7.1 %). The EOs obtained from targeted samples exhibited strong α-glucosidase inhibitory activity. These results are encouraging and underline that the EOs of Eucalyptus species may be a promising alternative source of natural antidiabetic.

Chemical Diversity and α-Glucosidase Inhibitory Activity in Needles Essential Oils of Four Pinus Species from Northwestern Himalaya, India

This work describes the study of the chemical profiling and α-glucosidase inhibitory activity of essential oils (EOs) from four Pinus species (P. wallichiana, P. patula, P. roxburghii and P. gerardiana). The identification and quantification of EOs metabolites were performed by GC/MS, GC-FID and ¹³ C-NMR. The needles of P. wallichiana and P. gerardiana presented the highest oil yields (0.35 % and 0.36 %, respectively). Twenty-four constituents were characterized in among samples exhibiting 93.8-97.7 % of the total EOs. The components and yields of the targeted samples were varied according to the species. Major components of the oils were α-pinene (20.5-34.1 %), β-pinene (1.4-53.0 %), δ-3-carene (0.2-47.0 %), limonene (1.7-13.4 %), β-phellandrene (0.2-23.4 %), β-myrcene (1.8-7.2 %) and α-terpinolene (0.6-7.9 %). The extracted EOs showed strong α-glucosidase inhibitory activity, which was close to the positive control, acarbose. This study showed that the EOs of Pinus species may be used as natural antidiabetic.