Comparison of Content in Phenolic Compounds, Polyphenol Oxidase, and Peroxidase in Grains of Fifty Sorghum Varieties from Burkina Faso

Abstract

Analysis of fifty sorghum [Sorghum bicolor (L.) Moench] varieties used in Burkina Faso showed that they have different contents of phenolic compounds, peroxidase (POX), and polyphenol oxidase (PPO). Most of the varieties (82%) had a tannin content less than 0.25% (w/w). POX specific activity was higher than the monophenolase and o-diphenolase specific activities of PPO. For POX, there was a diversity of isoforms among varieties. No clear correlation could be made between the quantitative composition of the grain in phenolics, PPO, and POX, and resistance of plant to pathogens. In general, varieties good for a thick porridge preparation ("tô") had low phenolic compounds content and a medium POX activity. From the red varieties, those used for local beer ("dolo") had a high content in phenolic compounds and PPO, and a low POX activity. The variety considered good for couscous had a low POX content. The characteristics might be useful as selection markers for breeding for specific applications.

Impact of Phenolic Compounds and Related Enzymes in Sorghum Varieties for Resistance and Susceptibility to Biotic and Abiotic Stresses

“…For convenience, the sorghum varieties were classified in alphabetic order of their name followed by arabic numbers: V1 to V50 (Table 1). Mature grains (Q60 days after anthesis) were harvested, surface-sterilized, and germinated as described previously (Dicko et al, 2002(Dicko et al, , 2005a. Germinated and ungerminated sorghum grains were dried, ground, and stored (Dicko et al, 2005a).…”

“…Extraction and Quantification of Phenolic CompoundsR Sorghum phenolic compounds were extracted and quantified as previously described (Dicko et al, 2002(Dicko et al, , 2005a. Results were expressed as phenolic equivalent per gram of flour (w/w), on dry matter basis.…”

“…previously (Dicko et al, 2002(Dicko et al, , 2005b. Enzyme extracts were prepared by mixing 250 mg of sorghum flour with 1.2 ml of 50 mM TrisYHCl buffer (pH 7.3) containing 0.5 M CaCl 2 and 2% (w/v) polyvinylpyrrolidone, at 4-C for 1 hr.…”

“…Commercial sodium trans-cinnamate was used as standard. The spectrophotometric assay for PPO was performed as described previously (Dicko et al, 2002). 4-Hydroxyanisole (4-HA) and 3,4-dihydroxyphenylpropionic acid (DHPPA) were used as substrates to determine the monophenolase and o-diphenolase activities of PPO, respectively.…”

“…Prior to determination of POX activity, extracts from ungerminated and germinated sorghums were diluted 400-and 1000-fold, respectively, in 50 mM TrisYHCl, pH 7.3, containing 0.5 M CaCl 2 and 1 mg/ml bovine serum albumin. POX activity was measured spectrophotometrically by monitoring the H 2 O 2 -dependent oxidation of ABTS, at 25-C (Dicko et al, 2002). The reaction mixture consisted of 10 ml of 200-fold diluted crude enzyme extract, 20 ml of 100 mM ABTS, 10 ml of 100 mM H 2 O 2 , and 160 ml of 50 mM sodium acetate, pH 4.0.…”