Composition of volatile organic compounds in flowers of Astragalus sahendi

Recent reports in the biggest herbal genus, Astragalus, in Iran; with a special viewpoint on tragacanth gum production

This comprehensive review was carried out to integrate all the data published in the electronic databases (Scopus, etc.) over the past two decades about the distribution, phytochemistry, ethnopharmacology, and pharmacology of Astragalus L. Although Astragalus is one of the largest genera of flowering plants in Iran, limited phytochemical screening of this genus has been reported. Cycloartane triterpene glycosides, labdane diterpenoids, flavonoids, and polysaccharides are the major identified compounds. Pharmacological studies revealed significant properties such as anti-inflammatory, anticancer, antidiabetic, etc. Moreover, ethnopharmacological studies of Astragalus sp. showed that this genus is used for gastrointestinal, fractures, joint pains, and skin problems in different localities of Iran. Tragacanth gum, as the main product of some Astragalus sp. with economic value, shows proper biological activities and uses as an emulsifier in food industries. This review might be helpful for researchers to find new chemical entities responsible for its claimed traditional uses and food supplements.

GC-MS Based Identification of the Volatile Components of Six Astragalus Species from Uzbekistan and Their Biological Activity

The compositions of volatile components in the aerial parts of six Astragalus species, namely A. campylotrichus (Aca), A. chiwensis (Ach), A. lehmannianus (Ale), A. macronyx (Ama), A. mucidus (Amu) and A. sieversianus (Asi), were investigated using gas chromatograph-mass spectrometry (GC-MS) analysis. Ninety-seven metabolites were identified, accounting for 73.28, 87.03, 74.38, 87.93, 85.83, and 91.39% of Aca, Ach, Ale, Ama, Amu and Asi whole oils, respectively. Sylvestrene was the most predominant component in Asi, Amu and Ama, with highest concentration in Asi (64.64%). In addition, (E)-2-hexenal was present in a high percentage in both Ale and Ach (9.97 and 10.1%, respectively). GC-MS based metabolites were subjected to principal component analysis (PCA) and hierarchal cluster analysis (HCA) to explore the correlations between the six species. The PCA score plot displayed clear differentiation of all Astragalus species and a high correlation between the Amu and Ama species. The antioxidant activity was evaluated in vitro using various assays, phosphomolybdenum (PM), 2,2 diphenyl-1-picryl-hydrazyl-hydrate (DPPH), 2,2-azino bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing power (FRAP) and ferrous ion chelation (FIC) assays. In addition, the potential for the volatile samples to inhibit both acetyl/butyrylcholinesterases (AChE, BChE), α- amylase, α-glucosidase and tyrosinase was assessed. Most of the species showed considerable antioxidant potential in the performed assays. In the DPPH assay, Ama exhibited the maximum activity (24.12 ± 2.24 mg TE/g sample), and the volatiles from Amu exhibited the highest activity (91.54 mgTE/g oil) in the ABTS radical scavenging assay. The effect was more evident in both CUPRAC and FRAP assays, where both Ale and Ama showed the strongest activity in comparison with the other tested species (84.06, 80.28 mgTE/g oil for CUPRAC and 49.47, 49.02 mgTE/g oil for FRAP, respectively). Asi demonstrated the strongest AChE (4.55 mg GALAE/g oil) and BChE (3.61 mg GALAE/g oil) inhibitory effect. Furthermore, the best tyrosinase inhibitory potential was observed for Ale (138.42 mg KAE/g). Accordingly, Astragalus species can be utilized as promising natural sources for many medicinally important components that could be tested as drug candidates for treating illnesses such as Alzheimer's disease, diabetes mellitus and oxidative stress-related diseases.

Ontogenetic Variation of Total Phenolics and Antioxidant Activity in Roots, Leaves and Flowers of Astragalus compactus Lam. (Fabaceae)

INTRODUCTION

The potential health risks and toxicity of synthetic antioxidants resulted in an upsurge of interest in phytochemicals as new sources of natural antioxidants. Phenolics of Astragalus L. (Fabaceae) possess antioxidant properties and have been shown to have a protective effect against several degenerative diseases. The objective of this study was to determine total phenolics and antioxidant activity of methanolic extracts from different parts of A. compactus Lam. at different phenological phases and to investigate the correlations between antioxidation and the contents of the total phenolics.

METHODS

Total phenolic content (TPC) was determined using the Folin-Ciocalteau reagent and the antioxidant capacity was evaluated with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) test.

RESULTS

Generally, the TPC in leaves was higher than that of the roots and flowers. TPC in leaves, roots and flowers of the species varied from 5.01-8.25, 4.29-7.89 and 4.19 μg GAE/mg DW, respectively. In addition, roots and leaves at fructification stage possessed higher TPC than vegetative and flowering stages. Therefore, the leaf extracts at fructification phase showed the highest TPC that accompanied with best antioxidant activity. In the root extracts, fructification stage was also characterized by the highest antioxidant activity.

CONCLUSION

A positive relationship between antioxidant activity and TPC showed that phenolics were the dominant antioxidant components in the species. The results obtained suggest that A. compactus methanolic extracts may serve as potential sources of natural phenolic antioxidants and that the fructification phase could be considered as the best stage for the harvesting of this plant.

Identification of volatile organic compounds in flowers of Astragalus lagopoides

Composition of volatile organic compounds (VOCs) in flowers of Astragalus lagopoides was studied using a hydrodistillation extraction procedure coupled with gas chromatography-mass spectrometry. The analyses allowed the identification of a number of 25 compounds, among which the presence of several bioactive aromatic derivatives such as guaiacol, eugenol, linalool, α- and 4-terpineol as well as nerol was attention-grabbing. Moreover, some other compounds like cyclohexane, 2-bromoethyl with repellent function also appeared to be present in the flower. As a result, the floral VOCs profile of A. lagopoides might reflect an adaptation to attract specialised pollinator insects. These findings provide important information for advances in understanding the ecological and evolutionary perspectives of pollination biology of the giant genus Astragalus.