Comparison Of Extracts Of Polyphenol

Comparison of extracts prepared from plant byproducts using different solvents and extraction time Brigita Lapornik

,

, Mirko Prošek and Alenka Golc Wondra

National Institute of Chemistry, Laboratory for Food Chemistry, Hajdrihova 19, 1001 Ljubljana, p.p. 660, Slovenia Received 31 May 2004; accepted 24 October 2004. Available online 8 December 2004.

Abstract By-products obtained after red fruit processing still contain large amounts of polyphenols, especially anthocyanins which act as antioxidants. The effect of solvent and extraction time on the yield of extracted antioxidants from grape, black and red currant by-products (marc) was investigated. Ethanol and methanol extracts of red and black currant contain twice more anthocyanins and polyphenols than water extracts, extracts made from grape marc had seven times higher values than water extracts. In water extracts the yields of polyphenols decreased, while in methanol and ethanol extracts their content increased with the time of extraction. The highest antioxidant activity was in extracts made from black currant marc, the lowest was in extracts made from

red currant marc. Grape extracts had high antioxidant activity due to its high content of polyphenols. Keywords: By-product; Marc; Extract; Red currant; Black currant; Grape; Polyphenols ; Anthocyanins; Antioxidant activity

Article Outline 1. Introduction 2. Experimental 2.1. Chemicals 2.2. Material 2.3. Extracts preparation 2.4. Measurement of total polyphenols 2.5. Measurement of total anthocyanins using pH differential method 2.6. HPLC analysis of individual anthocyanins 2.7. Measurement of total antioxidant activity using DPPH test 2.8. Measurement of total antioxidant activity using β-carotene test 2.9. Statistical analysis 3. Results 3.1. Influence of plant material, solvent and extraction time on yield of polyphenols and anthocyanins in extracts 3.2. Influence of plant material, solvent and extraction time on antioxidant activity in extracts 4. Discussion 5. Conclusions References

Fig. 1. Chemical structure of anthocyanidins (DeMan, 1999).

Table 1. Concentration (mg/l) of total polyphenols measured in extracts prepared from black currant, red currant and grape marc with different solvents and different extraction time

Table 2. Concentration (mg/l) of total anthocyanins measured in extracts prepared from black currant, red currant and grape marc with different solvents and different extraction time

Table 3. Relative percent (%) of individual anthocyanins in red currant marc extracts of total anthocyanins (mg/l) determined by HPLC method

Dp—Delphinidin; Cy—Cyanidin; G—glucose; sopho—sophorose; sam— sambubiose; xyl—xylose; R—rutinose.

Table 4.

Relative percent (%) of individual anthocyanins in black currant marc extracts of total anthocyanins (mg/l) determined by HPLC method

Dp—Delphinidin; Cy—Cyanidin; G—glucose; R—rutinose.

Table 5. Relative percent (%) of individual anthocyanins in grape marc extracts of total anthocyanins (mg/l) determined by HPLC method

Dp–Delphinidin; Cy–Cyanidin; G–glucose; Pt–Petunidin; Pe–Peonidin; Mv– Malvidine.

Table 8. Sources of variability and significance on content of total polyphenols, anthocyanins, antioxidant activity (DPPH) and antioxidant activity coefficient (beta-carotene)

P

0.001 statistically very high significant influence; P

significant influence; P

0.05 statistically significant influence; P > 0.05

statistically not significant influence.

Table 6.

0.01 statistically high

Antioxidant activity (%) of extracts prepared from black currant, red currant and grape marc with different solvents and different extraction time

Table 7. Antioxidant activity coefficient (CAA) of extracts prepared from black currant, red currant and grape marc with different solvents and different extraction time

Table 9. Correlations between content of total polyphenols, content of total anthocyanins, antioxidant activity (% AA) and antioxidant activity coefficient (CAA) for tested extracts