Neutral Constituents of Alcea rosea Leaves

Abstract

Plants of the family Malvaceae are distinguished among leafy plants by high contents of polyprenols in the aerial parts [1][2][3][4]. In continuation of research on polyisoprenoids from plants of this family, we report the polyisoprenoid compositions of two varieties of Alcea rosea L. (rose hollyhock, 1, and ruby hollyhock, 2) growing in Samarkand Province. Plant material was collected on Aug. 26, 2011 during fruiting in Pai Aryk District.Alcea rosea L. is a beautiful garden flower that numbers ~60 varieties distributed in the eastern Mediterranean region, the Middle East, and Central Asia [5]. Flowers of the plant are used in medicine to ameliorate coughing. Various aqueous decoctions and infusions of the plant are used as mucosal, softening, binding, and anti-inflammatory agents [6].Alcohol extracts of the dried and ground plant leaves were obtained by the literature method [7] in yields of 22.5 and 23.2%, respectively. The alcohol extracts were condensed to 1/3 the volume and worked up with weak NaOH solution in order to remove free acids. The residue was saponified as before [8] to isolate total neutral substances (NS) in yields of 8.5% [1, with polyprenol (PP) content 84.7%] and 8.25% (2, with PP content 80.7%) of the air-dried mass (ADM). Then, column chromatography separated the obtained total NS from A. rosea leaves. The adsorbent was KSK silica gel (60-100 mesh); mobile phase, petroleum ether-Et 2 O mixtures (50:1, 30:1, 25:1). Fractions (100 mL) were collected and monitored by TLC. Identical fractions were combined. PP fractions were isolated. The PP yield for 1 was 1.88% (of ADM); for 2, 1.76%. Furthermore, hydrocarbon, triterpenoid, and phytol fractions were isolated. These were identified by preparative TLC as before [9]. PP fractions were analyzed using an Agilent 1100 chromatograph with an Eclipse XDB-C-18 column (0.46 u 150 mm) with UV detection at 210 nm. The mobile phase was a gradient (%B); 0-20 min, 0-75; 20-25 min, 75-100; 25-30 min, 100-0 at flow rate 0.75 mL/min. The analysis time was 30 min. The mobile-phase gradient consisted of systems A (MeOH-H 2 O, 9:1, v/v) and B (MeOH-hexane-i-PrOH, 2:1:1) [9]. PP from cotton leaves with a known composition were used as standards [10]. Table 1 presents the HPLC analytical data. Table 1 shows the constituent ratio of the rose and ruby hollyhock leaf fractions in addition to the PP in each sample. It can be seen that undecaprenol (n = 11) and dodecaprenol (n = 12) dominated the PP-homologs. The decaprenol (n = 10) content in rose hollyhock was 9.4%; in ruby, 8.2%. The tridecaprenol fractions were identical at 8.6%.The other constituents of NS from A. rosea (rose hollyhock) were identified on an Agilent 7890 GC-5975 without additional separation by comparing their retention times with those of known compounds and comparing the mass spectra with hose in the NIST 02MS electronic library. The accuracy of identification was 75-90%. Table 2 presents the results. Table 2 shows that the principal components of the NS were E-sitosterol (20.9%), phytol (20.55%),...