Simultaneous determination of flavonoids and phenylethanoids in the flowers of Verbascum densiflorum and V. phlomoides by high-performance liquid chromatography.

INTRODUCTION: Mullein (Verbascum) flowers are highly valued herbal drugs used in the treatment of inflammation, asthma, spasmodic coughs and other respiratory tract diseases. Their phenolic constituents are considered to be responsible for the anti-inflammatory and antimicrobial activity of the herb. However, knowledge about the contents of phenolics in flowers is limited and no HPLC method for their analysis is available. OBJECTIVE: To develop and validate an RP-HPLC-UV method for the simultaneous determination of eight flavonoids and two phenylethanoids in the flowers of Verbascum densiflorum and V. phlomoides. METHODOLOGY: HPLC separation was accomplished on a C(18) Lichrosphere 100 column (5 microm, 250 mm x 4.6 mm, i.d.) with an acetonitrile gradient elution using aqueous 0.5% (w/v) orthophosphoric acid solution containing 1% (v/v) tetrahydrofurane. RESULTS: All the calibration curves showed good linear correlation coefficients (r > 0.997) over the wide test ranges. The relative standard deviation of the method was less than 3.4% for intra- and inter-day assays, and the average recoveries were between 93.5 and 101.9%. High sensitivity was demonstrated with detection limits of 0.062-0.083 microg/mL for flavonoid aglycones, 0.156-0.336 microg/mL for flavonoid glycosides and 0.390-0.555 microg/mL for phenylethanoids. The flower samples of V. phlomoides were found to contain high levels of diosmin and tamarixetin 7-rutinoside (2.327-2.392% of dry weight), whereas verbascoside (0.688-0.742% of dry weight) and luteolin 7-glucoside (0.204-0.279% of dry weight) dominated in the V. densiflorum flower. CONCLUSION: The HPLC method established is appropriate for the quality assurance and the differentiation of V. phlomoides and V. densiflorum samples.

Flavonoids and phenolic acids of Nepeta cataria L. var. citriodora (Becker) Balb. (Lamiaceae).

Luteolin 7-O-glucuronide, luteolin 7-O-glucurono-(1-->6)-glucoside, apigenin 7-O-glucuronide as well as free aglycones luteolin and apigenin have been isolated from lemon catnip herb (Nepeta cataria L. var citriodora). Luteolin 7-O-glucurono-(1-->6)-glucoside is probably a new compound, for the first time described. Two minor constituents of flavonoid fraction have been identified as apigenin 7-O-glucoside and luteolin 7-O-glucoside by means of HPLC method. The percentage of total flavonoids determined by use of spectrophotometric method was in the range from 0.30 to 0.46% of dry mass. In phenolic acid fraction, caffeic, rosmarinic and p-coumaric acids have been identified. Total amount of phenolic acids determined by spectrophotometric method was in the range of 0.75% to 1.4 % and the content of rosmarinic acid quantified by HPLC method fluctuated in the wide range from 0.06% to 0.15% depending on the sample. The results of the investigations showed that the composition of flavonoid compounds and phenolic acids in lemon catnip are similar to those in lemon balm (Melissa officinalis L.). The amount of flavonoids are similar in both plants, and the percentage of rosmarinic acid is about ten times lower in lemon catnip than in lemon balm. The presence of luteolin, apigenin and their glycosides, caffeic acid as well as the previously described terpenoids (ursolic acid, citral, nerol. geraniol) suggests the possibility of the use of lemon catnip herb as a constituent of phytopharmaceutical preparations with mild sedative, antispasmodic, antioxidative and antiinflammatory action.

The content of lignan glycosides in Forsythia flowers and leaves.

Quantitative determination of lignan glucosides in flowers and leaves of three taxons of Forsythia Vahl was performed using the HPLC method. The main lignan compound in the flowers of F. suspensa appeared to be (+)-pinoresinol beta-D-glucopyranoside, whereas in the leaves of this species phillyrin was the predominant lignan. The content of (+)-pinoresinol beta-D-glucopyranoside in F. suspensa flowers amounted to 4.3-7% and that of phillyrin did not reach 1%. The inverse ratio of (+)-pinoresinol beta-D-glucopyranoside to phillyrin occurred in the leaves of F. suspensa, which contained up to 4.3% of phillyrin and 1.6% and less (+)-pinoresinol beta-D-glucopyranoside. The flowers of F. viridissima and F. x intermedia were rich in arctiin: 5.5-10.2% and up to 11.5%, respectively. The leaves of these two species contained less arctiin: up to 4.3% in F. viridissima and up to 2.3% in F. x intermedia. The flowers showed the highest level of lignans at the phase of buds, it decreased during the blooming time.

Isolation and identification of biologically active compounds from Forsythia viridissima flowers.

Flavonol glycosides, rutin and isoquercitrin, lignan glycosides, arctiin and matairesinoside, as well as phenylethanoid verbascoside (= acteoside), ursolic acid and beta-sitosterol have been isolated from the flowers of Forsythia viridissima. Two other isolated substances were characterized respectively as a wax and a hydrocoloidal polysaccharide consisting of galactose, galacturonic acid, arabinose, glucose, xylose, and rhamnose.