International Journal of Drug Development and Research

Keywords

Cassia species, flavonoids, phenolics, Gallic acid, Quercetin.

INTRODUCTION

Phenols, sometimes called phenolics are secondary metabolites that are synthesized by plants during normal development and in response to stress conditions such as infection, wounding, UV radiation [4] [23]. These compounds occur ubiquitously in both edible and non-edible plants[11,13] and are a diversified group of phytochemicals derived from phenyl alanine and tyrosine and have been reported to have multiple biological activities.[7][8][9][6] . Plant phenolics include simple phenols, phenolic acids (both benzoic and cinnamic acid derivatives), coumarins, flavonoids, stilbenes, hydrolysable and condensed tannins, lignans and lignins. In plant, phenolics may act as phytoalexins, antifeedants, attractants for pollinators, contributors to the plant pigmentation, antioxidants and protective against Ultraviolet light, among others. Phenolics in general contribute to the bitterness, astringency, color, flavor, odor, oxidative stability of products in addition to health-protecting capacity of some.

Flavonoids, the most common group of polyphenolic compounds are widely distributed in fruits, vegetables, nuts, seeds, herbs, spices, stems, flower, tea and red wine imparting bright colors that make the biosphere beautiful[2][15] . These are some ten classes of flavonoids recognized-anthocyanins, proanthocynidine, flavonols, flavones, glycoflavones, biflavonlys, chalcones, aurones, flavanones and isoflavones.[16]. These display a remarkable array of biochemical and pharmacological actions viz., antinflammatory, antioxidant, antiallergic, hepatoprotective, antithrombic, antiviral and anticarcinogenic activites.[21][19].

These compounds appear to play vital role in defence against pathogens and predators hence contribute to the physiological functions such as seed maturation and dormancy.[25]. They are synthesized from phenyl propanoid and acetate derived precursors[18]. Flavonoids are considered to be of interest to human beings because of their potent antioxidant activity and the beneficial effects they have on human health in fighting diseases. The capacity of flavonoids to act as antioxidants depends upon their molecular structure. The position of hydroxyl groups and other features in the chemical structure of flavonoids are important for their antioxidant and free radical scavenging activity[17][12][5].

MATERIALS AND METHODS

Processing of plant material for solvent extraction:

All the 12 species of Cassia viz., Cassia alata, Cassia auriculata, Cassia fistula, Cassia hirsuta, Cassia kleini, Cassia occidentalis, Cassia polyphylla, Cassia serecea, Cassia siamea, Cassia spectabilis, Cassia surratensis and Cassia tora were collected fresh from in and around Bangalore, washed thoroughly and shade dried. All the 12 plants were authenticated by the Senior Scientist, Department of CES (Centre for Ecological Studies), IISc, Bangalore and Plantation officer, Lalbagh Botanical Gardens, Bangalore. The dried leaves were then pulverized into a fine powder and stored in dark bottles until use

Preparation of extracts:

The powdered leaf material packed in the soxhlet apparatus (15gms) was subjected to continous percolation with methanol at 40oC.The extract was then evaporated using a rotary evaporator to have concentrated methanol extracts. The concentrated dark brown sticky solid mass of extract were stored in air tight screw cap vials and kept in refrigerator till further use[24].

Quantitative phytochemical screening:

Determination of total phenolic contents in the plant extracts:

The concentration of phenolics in plant extracts was determined using spectrophotometric method[1] with a little modification. Methanolic solution of the extract in concentration of 10gm/ml was used in the analysis. The reaction mixture was prepared by mixing 0.05ml of methanolic solution of the extract, 0.2ml of (1:5) Folin Cicolteau reagent and 4ml of 20% Na2CO3. Blank was concomitantly prepared. The samples were thereafter incubated at room temperature for 30 minutes. The absorbance was determined using spectrophotometric at Hmax=750nm. The samples were prepared in triplicate for each analysis and the mean value of absorbance was obtained. The same procedure was repeated for the standard solution of Gallic acid and the calibration line was constructed. Based on the measured absorbance, the concentration of phenolics was read (mg/ml) from the calibration line, then the content of phenolics in extracts was expressed in terms of Gallic acid equivalent (mg of Gallic acid of extract)[22].

Determination of flavonoid concentration in the plant extracts:

The content of flavonoids in the examined plant extracts was determined using spectrophotometric method[3]. The sample contained 0.05ml of the methanol solution of the extract in concentration of 10mg/ml and 0.1ml of 10% Al2Cl3 solution, 0.1ml of 1M potassium acetate, 2.8ml distilled H2O, 1.95 ml of methanol. The samples were incubated at room temperature for 30min. The samples were prepared in triplicate for each analysis and the mean value of absorbance was repeated for the standard solution of Quercetin and the calibration line was constructed. Based on the measured absorbance, the concentration of flavonoids was read (mg/ml) on the calibration line, then the content of flavonoids in extracts was expressed in terms of Quercetin equivalent (mg of Quercetin/gm of extract)[22].

RESULTS AND DISCUSSIONS

Methanol extracts of all the 12 species of Cassia were prepared to study the total flavonoid and phenolic content. The yield of extract obtained from 15gm of dry plant material was measured for each extract (Table:1).

The total phenolic content in the plant extracts was examined using Folin-Ciocalteus reagent and is expressed in terms of Gallic acid equivalent.The values obtained for the concentration of total phenolics are expressed as mg of GA/g of extract. The total phenolic content in the examined extracts ranged from 61.77 to 174.34 mg GA/g. The high concentrations of phenolics were obtained from methanolic extract of Cassia auriculata.

The total flavonoid content in the examined extract ranged from 4.96 to 52 mg QE/g. The highest concentration of flavonoid was measured in the methanolic extract of Cassia serecea.

CONCLUSION

The results showed that there are great differences among the 12 Cassia species regarding the content of flavonoid and phenolics. The present investigations revealed that the leaves of Cassia auriculata contain significantly high amount of phenolics and Cassia serecea showed high quantity of flavonoids. The objective of this study was to obtain a comparative account of the amount of phenolics and flavonoids present in these species.

Acknowledgement

The authors thank Dr. Thamiz Seran, Prof, Department of Botany, St. Joseph’s College, Post Graduate Centre and Centre for Research, for all his kind encouragement and support.

Tables at a glance

Table 1

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