Plant phenolic compounds known as plant biochemicalsthat have one or more hydroxyl groups attached to aromatic ring. 14. Thesecompounds are investigated due to their physiological and morphological characteristicsin plants. Such as, they play an active part in the defensive mechanismresponse of plants against herbivores, pathogens and stress situations.
Thesedefensive actions of secondary metabolites could represent a further method ofplant protection 9. They play a criticalrole in human diet and interested of their high antioxidant activities.Previous works revealed that, plant phenolic compounds have anti-allergenic,anti-artherogenic, anti-inflammatory and anti-microbial effects1.Large amounts of phenolic compounds have beenfound in apples. 13 The previous studies revealed that, apple skin showedhigher phenolic content than pulp extracts of apples. These divergence were dueto high levels of catechins and chlorogenic acid.
4 Phenolic compounds areclassified in many different sub-groups (simple phenolics, phenolic acids,cinnamic acids, coumarins and flavonoids) based on the number of carbon atomsin the molecule 14. Flavonoids are one of the most investigated class amongthe phenolic compounds due to their high biological acitivities. The extractionof the flavonoids are generaly made by chloroform, diethyl ether, ethyl acetateor dichloromethane. Flavonoids are responsible for different colors in theplant tissues such as blue, purple, yellow, orange and red color5. Theflavonoid family includes flavanones, flavanonols, leucoanthocyanidins,anthocyanins, anthocyanidins, and flavones.
14.Apples have beendiscovered as important source of polyphenols, however, the separation and classificationremained analytically difficult. The content of phenolic compounds in applesare the flavanol monomers, quercetin, glycosides, dihydrochalcones, esters ofcaffeic and p-coumaric acids with qunic acid 12.Thin LayerChromotography, known as TLC is a separation and identification method toinvestigate compounds. It is used in scientific area for qualitative analysisas it is economical, simple and quick method. It provides to analyse severalsamples on the same TLC plate in a short-time. There is mobile (solvent) andstationary phase (samples as spots or lines) in TLC. Silica-gel TLC method isthe most convenient method that is used to identify the phenolic acids andflavonoids from different plant species 11.
Flavonoids arepresent in plant tissues either as sugar conjugates or as aglycones. As thequantitative determination of flavonoid glycosides is difficult hydrolysationis used for quantification 7.HPLC (High Performance LiquidChromatography) is an analytical method which uses high pressure in order to mobilizethe sample (mobile phase) through the column filled with chromatographicpacking material, called stationary phase (SP). HPLC is a common used techniquefor both separation and quantification of plant phenolic compounds. HPLCsensitivity and detection is based on purification of plant phenolics andpre-concentration from complex matrices of crude plant extracts 6.