Biotransformation of quercetin, kaempferol and apigenin to monoglycosylated derivatives by in vitro suspension cultures of Astragalus vesicarius ssp. carniolicus

Biotransformation of exogenous substrates quercetin, kaempferol and apigenin by suspension cultures of Astragalus vesicarius ssp. carniolicus to their monoglycosylated derivatives was performed. The maximal enzymatic potential of cells of A. vesicarius ssp. carniolicus was evaluated by different concentrations of substrate exposure. According to quantitative ultra-high performance liquid chromatography-high resolution electrospray ionization mass spectrometry (UHPLC-HR-ESI-MS) analysis, the highest concentration of kaempferol O-glycoside (14.88 nmol/g dry weight, DW), apigenin O-glycoside (10.55 nmol/g DW) and quercetin O-glycoside (150.83 nmol/g DW) was achieved, when suspension cultures were treated with 4 mg/mL kaempferol, 4 mg/mL apigenin and 3 mg/mL quercetin, respectively. The glycosidic products of biotransformation were not detected in the untreated control

Flavonoids in in vitro cultures of Astragalus hamosus

Astragalus hamosus contains valuable biologically active compounds, incl. flavonoids. The possibility for in vitro cultivation of the species as a source of important flavonoids was studied. Shoot and callus cultures were established and successfully cultivated on different nutrition media, complemented or not with growth regulators. An ultra-high performance liquid chromatography – high-resolution electrospray ionisation mass spectrometry (UHPLC-HRESIMS) qualitative and quantitative analysis of non-purified methanol extracts of these cultures was performed. It was found that the cultures produced rutin in comparable quantity. Interestingly, both shoots and callus cultures accumulated the rare triglycosides alcesefoliside and mauritianin. The quantity of mauritianin, biosynthesized in shoots, was significantly higher to that in callus cultures. Alcesefoliside, was in lower quantity, compared to mauritianin. In addition, callus cultures produced alcesefoliside trice as the shoots, besides their lower level of differentiation. These findings could serve as initial research to establish the value of in vitro cultures from A. hamosus as an alternative mean of production of pharmaceutically important flavonol glycosides

In vitro production of flavonoids in cultures of Gypsophila glomerata

Effects of increased concentration of calcium chloride on growth and production of flavonoids in newly established shoot and callus Gypsophila glomerata cultures were studied. The highest impact of CaCl2 on the growth index was determined in callus cultures (GI = 0.92), while in shoot cultures calcium treatment reduced the amount of biomass (GI = 0.38). Total flavonoids in shoot cultures grown on MS medium and MS medium supplemented with double amount of CaCl2 were 0.36 mg/g d. w. In both callus cultures, 2 mg/g d. w. total flavonoids were quantified. Shoots and callus grown on non-modified media accumulated 0.02 mg/g d. w. quercetin derivatives. Unlike these, both shoots and callus grown on calcium-enriched media accumulated 0.03 and 0.05 mg/g d. w. of isorhamnetin derivatives. In vitro shoot cultures grown on MS medium enriched in twice the amount of CaCl2 accumulated the highest amount of saponarin (0.138 mg/mg d. w.)

Induction of flavonoid biosynthesis by in vitro cultivation of Astragalus glycyphyllos L.

Establishment of in vitro cultures from Astragalus glycyphyllos, determination of biomass and analysis of total flavonoids, rutin and camelliaside A were performed. To increase flavonoid production various combinations of plant hormones and light/dark regimen were investigated. Suspension cultures with exogenous quercetin were evaluated for possible increase in flavonoid production. Shoots, calli and suspensions were successfully established. Rutin and camelliaside A were proved in highest amount in shoots. Calli, cultivated on modified G48 medium, with double amount of Ca2+ and Mg2+, achieved higher total flavonoid content (2.37 and 2.03 mg/g DW). Suspensions cultures, cultivated on modified G48 medium with 10, 20 and 30 mg/mL quercetin achieved higher total flavonoid content (0.09, 0.10 and 0.13 mg/mg DW). Biotransformation of quercetin to isoquercitrin was achieved. The highest concentration of isoquercitrin (56.73 ng/mg DW) was observed on suspensions cultures cultivated on modified G48 medium, with 20 mg/mL quercetin

Antiproliferative activity of extract from in vitro callus cultures of Astragalus vesicarius ssp. carniolicus (A. Kern.) Chater

Five isoflavonoids, i.e. 5-hydroxy-7-methoxy-2’, 5’-dihydroxyisoflavone (AV4), 5, 7-dihydroxy-4’-methoxyisoflavone (AV6), 7-methoxy-5-hydroxy-4’-methoxy-2’-hydroxyisoflavone (AV7), 8-pregnyl genistein (AV9), 5,7-dihydroxy-8-pregnyl-4’-methoxy-2’-hydroxyisoflavone (AV10) and one coumarochromone – sophorophenolone (AV8) were isolated from EtOAc of in vitro callus cultures of Astragalus vesicarius ssp. carniolicus, after enzymatic hydrolysis with β-glucosidase. Their structures were tentatively elucidated by spectroscopic mean (1H NMR and HR-ESI-MS spectra). Antiproliferative activity of EtOAc extract and isolated aglycones against chemosensitive human promyelocyte cell line HL-60 and its multidrug-resistant variant HL-60/Dox was assessed in vitro. Despite the strong activity of EtOAc (IC50 8.8 µg/mL (HL-6, 72 h) to 11.8 µg/mL (HL-60/Dox, 72 h)), prenylated compound AV9 showed also antiproliferative activity – 36.1 µg/mL (HL-60 and HL-60/Dox, 72 h)