Flavonoids from leaves of Pyrus communis, Malus sylvestris, and Malus domestica

Abstract

Flavonoids form one of the most common groups of phenolic compounds and are widely distributed in the plant world. Hydroxyls in their molecules are responsible for their antioxidant activity, which is considered one of the required properties of drugs for treating such diseases as cancer, atherosclerosis, hypertension, infarct, etc. Flavonoids have a variety of effects on the human organism. They exhibit capillary strengthening, antioxidant, antiradiation, antitumor, anti-inflammatory, antiatherosclerotic, spasmolytic, hypotensive, estrogenic, and bactericidal activities. The main property of these compounds is their low toxicity and more often the lack of it [1, 2].We investigated leaves of common pear Pyrus communis L., wild apple Malus sylvestris L., and domestic apple M. domestica Borkh. varieties Antonovka, Glory, and Whitesap, which are widely used in folk medicine to treat various pathologies. The goal of our work was to isolate and identify flavonoids from these types of raw material [2].Ground and air-dried raw material was extracted with ethanol (50%) in a 1:10 (material:extractant) ratio. The aqueous alcohol extracts were combined and evaporated in vacuo to an aqueous residue. The resinous precipitate that formed on standing contained chlorophyll and was removed. The aqueous solution was treated successively with CHCl 3 , ethylacetate, and butanol. The ethylacetate and butanol fractions were evaporated to dryness and chromatographed over a polyamide column (d, 1.5; h, 50 cm) with elution by CHCl 3 and a CHCl 3 :EtOH mixture with a gradually increasing concentration of the latter to 20%. Thus, we isolated 18 compounds of flavonoid nature [3].The structures of the isolated compounds were elucidated using physicochemical, chemical, and biochemical analytical methods (PC and TLC; UV, IR, and PMR spectroscopy; optical activity; melting points; acid and enzymatic hydrolysis) [3].The products from acid hydrolysis of compound 2 contained according to chromatographic and physicochemical methods (acetylation, methylation, alkaline degradation, melting point, direct and differential UV spectroscopy using ionizing and complexing reagents) the aglycon phloretin; 6, apigenin; 8, luteolin; 10, kaempferol; and 12-16, quercetin. Compound 16 contained glucose and rhamnose; 2, 6, 8, 10, and 14, glucose; 12, galactose; 13, rhamnose; and 15, arabinose. The structures of the carbohydate substituents were elucidated using enzymatic hydrolysis by rhamnodiastase and grapevine snail enzyme.Acid hydrolysis of 1, 3, 4, 5, 7, 9, 11, 17, and 18 enabled them to be assigned as flavonoid aglycons. Their structures were elucidated by chromatography; alkaline degradation; acetylation; methylation; UV, IR, and PMR spectroscopy; and melting point [3][4][5][6][7].Thus, the investigations of the compounds isolated from leaves of pear and apple varieties identified them as the following. 1, C 15 H 14 O 5 , mp 257°C, λ max 225, 286 nm; 3-(4-hydroxyphenyl)-1-(2,4,6-trihydroxyphenyl)-1-propanone or phloretin; 2, C 21 H 24 O 10 , mp 170-171°C, λ...

Characterization of the Polyphenolic Profiles of Peel, Flesh and Leaves of Malus domestica Cultivars Using UHPLC-DAD-HESI-MSn

“…Besides phloridzin (12) and phloretin (16), that were confirmed using standards, three other phloretin derivatives were also characterized in all apple cultivars (assigned as peaks 13, 14 and 15). According to their UV spectra, these compounds can be described as phloretin derivatives, whereas the comparison of MS data with those found in literature [18][19][20][21] [22].…”

“…The same groups of flavonoids present in apple peel and flesh were also found in the leaves, which also had flavones. Polyphenols in apple leaves (caffeic acid, isoquercetin, quercetin, kaempferol, apigenin-7-O-glucoside, apigenin, luteolin and myricetin) have been suggested as taxonomic markers for identification of Malus L. and Pyrus L. genera [12]. Accumulation of polyphenols has been shown as a post infection response to parasites such as scrubs [12,13].…”

“…Many studies on polyphenols in apple fruits have been reported [5][6][7][8][9][10][11], some of them comparing the polyphenol content of peel and flesh, which is considered important since apples are consumed with and without peel. However, data on the polyphenolic profile of the leaves of apple trees are limited even though it has been shown that their composition might be used as a variety marker as well as an indicator of the health condition of the apple tree [12,13].…”

“…The polyphenolic compounds detected in all studied samples were classified into five groups: phenolic acids, flavаn-3-ols, flavonols, dihydrochalcones and flavones. Sixteen of them were unambiguously identified by comparing retention times (t R ), UV and MS data with those of the available standards (peaks 1,3,5,6,8,10,11,12,16,17,[22][23][24][25][26][27]. Identification of another 11 polyphenolic compounds, for which standards were not available, was based on the UV absorption and MS data for the deprotonated molecules and their fragmentation pathways [M-H] -(data in Table 1).…”

“…Five major groups of polyphenolic compounds have been characterized in apple fruits: monomeric flavan-3-ols (catechins), polymeric flavan-3-ols (procyanidins), dihydrochalcones (phloretin glycosides), flavonols (quercetin glycosides), hydroxycinnamic acid derivatives and anthocyanins (mainly cyanidin glycosides) present in the red varieties [8,14]. Apple leaves contain mostly flavonols, few procyanidins, hydroxycinnamic acids, and dihydrochalcones such as phloridzin and phloretin and their derivatives [12,13]. Unlike from the flesh and the peel, apple leaves also contain flavones [13].…”