J. Sci. Ind. Res. B.
(India) 16, 154 (1957)
Survey of Anthoxanthins: Part X—A Note on the Anthoxanthins of Red & Yellow Roses
S. R. GUPTA, (Miss) K. S. PANKAJAMANI & T. R. SESHADRI
Department of Chemistry, University of Delhi, Delhi
(Manuscript received 7 December 1956)
Yellow roses have been found to be rich in flavonol glycosides. In a large number of cases kaempferol is the predominant component, but in a few cases considerable quantities of quercetin are also present. Red roses also contain appreciable amounts of flavonol mixtures as glycosides. Kaempferol and quercetin are invariable components of both types of roses and myricetin is occasionally present. The presence of flavonol glycosides in considerable quantity may account for the use of rose petals as laxatives. They are also good sources of vitamin P.
GENERAL methods of characterization and separation of flavonols present in plant materials have been described in Parts I1 and 1I2 of the present series. In subsequent work the anthoxanthin components of the flowers of a number of plants were examined. The results of similar studies on red and yellow varieties of roses are reported in the present communication.
Red roses — Red roses are noted for their contents of anthocyanins; however, Karrer and Schwarz3 reported the isolation of quercetin from a sample of the petals of Rosea rubrae. Important varieties of red roses available in Delhi have now been examined and found to contain appreciable quantities of anthoxanthins.
Petals of the fresh winter flowers were extracted with hot alcohol, hydrolysed with mineral acid, the crude aglycones taken up in ether and analysed by circular paper chromatography using phenol-water (lower layer) as the solvent. Though the anthocyanins present in the red flowers are also extracted by alcohol, after the hydrolysis only the flavonols are taken up by ether and the anthocyanidins are left behind. Among all the varieties examined a maximum of three rings was met with. The innermost ring had Rf 0.33 and indicated the presence of myricetin; the next had Rf 0.57 corresponding to quercetin and the outermost had Rf 0.79 corresponding to kaempferol. No other entities could be detected. The yields of the total flavonols are given on the basis of fresh flowers; in general they have to be multiplied by 5 in order to get the value on the air-dry matter. Kaempferol and quercetin are invariably present (Table 1).
Yellow roses — In an earlier publication1 two horticultural varieties of yellow roses, Marechal Niel and Lady Hillingdon, were examined and found to contain predominantly kaempferol with traces of quercetin in the combined form as glycosides. They were, therefore, considered to be convenient sources of kaempferol. Some other types of yellow roses have now been collected and an examination of their flavonoid composition has been carried out using circular chromatography. These flowers are found to be rich in flavonoid pigments, sometimes of the order of 3 per cent of the fresh flowers (15 per cent of air-dried matter) (Table 2). Since they seem to be markedly free from wax and resin, the isolation of the pigments in a pure state is easy and convenient. In the majority of cases, kaempferol is the predominant component along with traces of quercetin. After one crystallization from alcohol, kaempferol can be obtained pure. In a few cases considerable amounts of quercetin occur and separation has to be undertaken. For the separation of such mixtures of quercetin and kaempferol the following methods were discussed earlier1,2: (1) fractional precipitation using neutral and basic lead acetates, (2) fractional crystallization of acetates, and (3) column chromatography of methyl ethers. Aqueous sodium borate has now been used for this purpose and found to be quite suitable; the separation is rapid. It has been used earlier4 for the separation of kaempferol from herbacetin. An ether solution of the crude aglycone mixture is shaken up with aqueous borax (pure, 5 per cent). Quercetin is extracted yielding a yellow solution with green fluorescence and is precipitated on acidification; kaempferol is recovered from the ether solution by evaporation of the solvent.
TABLE 1 — ANTHOXANTHIN CONTENTS OF SOME RED ROSES
|Advocate||Rich crimson shade deeply veined, the base petals bright red||0.5||C (+)|
|Betty||Coppery red, shaded with yellow||0.8||A (+)|
|Charles K. Douglas||Scarlet, flushed with velvety crimson||0.6||A (+)|
|Clovelly||Carmine roses||1.0||A (+)|
|Dean Hole||Silvery carmine, shaded with salmon||0.7||C (+)|
|Etoile de Holland H.T.||Bright dark red shade||0.6||B (-)|
|Fred J. Harrison||Cardinal red, suffused crimson||0.8||A (+)|
|Hadley||Dark red||1.0||C (+)|
|Lamia||Reddish orange||1.0||C (-)|
|Margaret Spaull||Orange||0.6||C (+)|
|Madame Edourd Herriot||Brilliant coral red||0.8||A (+)|
|Mrs. A. R. Waddell||Rosy scarlet buds opening to reddish salmon||1.0||A (+)|
|Picture||Orange colour||1.0||C (-)|
|Una Wallace||Soft cherry rose||0.7|| Myricetin
A, kaempferol major constituent and quercetin minor constituent; B, quercetin major constituent and kaempferol minor constituent; C, both kaempferol and quercetin in equal amounts; (+) or (-) indicate the presence or absence of myricetin which occurs in traces only.
TABLE 2 — ANTHOXANTHIN CONTENTS OF SOME YELLOW ROSES
|Angele Pernet||Vivid orange-yellow shaded reddish apricot||2.0||C (-)|
|Blanche Messing||Pinkish yellow||1.0||A (+)|
|Very pale yellow||0.8||A (-)|
|Dorina Neave H.T.||Silvery pink||1.3||A (+)|
|Golden Ophelia H.T.||Inner petals deep golden, outside ones paler||3.0||A (+)|
|Golden Gleam H.T.||Bright buttercup yellow||2.3||B (-)|
|Golden Spray||Yellow||0.8||B (-)|
|Lady Hillingdon H.T.||Fine orange yellow||1.3||A (+)|
|Lucile Barker||Rich apricot yellow||1.0||C (+)|
|Mabel Drew||Deep cream shaded passing to canary yellow in the centre||1.2||A (-)|
|Madame Jules Bouche||Salmon white, centre shaded with rose||0.8||C (-)|
|McGredy's Yellow||Yellow||1.2||A (+)|
|McGredy's Ivory H.T.||Cream ivory petals, base light yellow||0.8||B (-)|
|McGredy's Sunset||Outer petals butter yellow; inside chrome yellow||1.0||C (+)|
|Miss Willmott||Soft sulphury cream||1.5||A (-)|
|Pharisaer||Rosy white, centre deep salmon rose||1.0||A (+)|
|Roselandia H.T.||Deep golden yellow||1.0||A (-)|
|Sir Henry Segrave||Primrose yellow with chrome base||1.0||A (+)|
|Talisman||Rich shades of scarlet and gold||0.8||C (+)|
|Trigo||Rich yellow||0.8||C (+)|
A, B, C, (+) and (-) have the same significance as in Table 1.