Absorption and metabolism of the mycotoxin zearalenone and the growth promotor zeranol in Caco-2 cells in vitro

Scope: Zearalenone (ZEN) and α‐zearalanol (α‐ZAL, zeranol) were studied in differentiated Caco‐2 cells and in the Caco‐2 Millicell^® system in vitro to simulate their in vivo intestinal absorption and metabolism in humans. Methods and results: In addition to metabolic reduction/oxidation, extensive conjugation with glucuronic acid and sulfate of the parent compounds and their phase I metabolites was observed. The positional isomers of the glucuronides and sulfates were unambiguously identified: Sulfonation occurred specifically at the 14‐hydroxyl group, whereas glucuronidation was less specific and, in addition to the preferred 14‐hydroxyl group, involved the 16‐ and 7‐hydroxyl groups. Using the Caco‐2 Millicell^® system, an efficient transfer of the glucuronides and sulfates of ZEN and α‐ZAL and their phase I metabolites into both the basolateral and the apical compartment was observed after apical administration. The apparent permeability coefficients (P_app values) of ZEN, α‐ZAL and the ZEN metabolite α‐zearalenol were determined, using an initial apical concentration of 20 μM and a permeation time of 1 h. Conclusion: According to the P_app values, the three compounds are expected to be extensively and rapidly absorbed from the intestinal lumen in vivo and reach the portal blood both as aglycones and as glucuronide and sulfate conjugates in humans.     

Glucuronidation of curcuminoids by human microsomal and recombinant UDP-glucuronosyltransferases

Glucuronidation is an important pathway in the metabolism of curcumin, but the isoforms of uridine-5'-diphosphoglucuronosyltransferase (UGT) involved are not known. Here, we report on the glucuronidation of the three natural curcuminoids and their major phase I metabolites with microsomes from human liver and intestine as well as with human recombinant UGTs. Microsomes from human liver generated predominantly the phenolic and small amounts of the alcoholic glucuronide of each curcuminoid, whereas intestinal microsomes formed only the phenolic conjugates but with higher activities. The phenolic glucuronidation of the curcuminoids was predominantly catalyzed by hepatic UGT1A1 and intestinal UGT1A8 and 1A10, whereas UGT1A9, 2B7, and 1A8 exhibited high activities for hexahydro-curcuminoids. UGT1A9 was able to form the alcoholic glucuronide of each curcuminoid in addition to the phenolic conjugate. These data suggest that the gastrointestinal tract contributes substantially to the glucuronidation of curcuminoids in humans, which may have important implications for their pharmacokinetic fate in vivo.     

Aromatic hydroxylation is a major metabolic pathway of the mycotoxin zearalenone in vitro

Zearalenone (ZEN) is a common mycotoxin, for which only reductive metabolites have been identified so far. We now report that ZEN is extensively monohydroxylated by microsomes from human liver in vitro. Two of the major oxidative metabolites arise through aromatic hydroxylation and are catechols. Their chemical structures have been unambiguously determined by using deuterium‐labeled ZEN and by comparison with authentic reference compounds. Moreover, both catechol metabolites of ZEN were substrates of the enzyme catechol‐O‐methyl transferase. One of the monomethyl ethers represented the major metabolite when ZEN was incubated with rat liver slices, thus demonstrating that catechol formation also takes place under in vivo‐like conditions. Out of ten major human cytochrome P450 (hCYP) isoforms only hCYP1A2 was able to hydroxylate ZEN to its catechols with high activity. Catechol formation represents a novel pathway in the metabolism of ZEN and may be of toxicological relevance.     

Novel oxidative metabolites of the mycoestrogen zearalenone in vitro

The estrogenic mycotoxin zearalenone (ZEN) is known to get metabolized to the alpha-and beta-isomers of zearalenol, but no hydroxylation products of ZEN have yet been reported as metabolites in animals or humans. We have therefore incubated ZEN with microsomes from rat liver in the presence of a nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH)-regenerating system and analyzed the extracted metabolites with HPLC and GC-MS after trimethylsilylation. A total of 17 in vitro metabolites were observed. The two major metabolites were tentatively identified as monohydroxylated ZEN with the newly introduced hydroxyl group localized in the aliphatic macrocyclic ring. According to the GC-MS analysis, other six monohydroxylation products of ZEN were formed as minor metabolites, together with alpha-and beta-zearalenol and monohydroxylated zearalenols. Thus, ZEN has a considerable propensity for undergoing metabolic hydroxylation reactions in vitro, and the in vivo formation and biological properties of such oxidative metabolites should now be studied.     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

In vitro phase II metabolism of xanthohumol by human UDP-glucuronosyltransferases and sulfotransferases

Xanthohumol (XN) is the principal prenylated flavonoid of the hop plant and has recently gained considerable interest due to its potential cancer-chemopreventive effects. However, the metabolism of XN has not yet been investigated in detail. Therefore, we studied the in vitro phase II metabolism of XN using nine human recombinant UDP-glucuronosyltransferases (UGT) and five sulfotransferases (SULT). The identification of the metabolites formed was elucidated using HPLC with diode array detection as well as HPLC/API-ES MS. XN was efficiently glucuronidated by UGT 1 A 8, 1 A 9, and 1 A 10; further important UGTs were UGT 1 A 1, 1 A 7, and 2 B 7. With respect to the sulfation reaction, SULT 1 A 1*2, 1 A 2, and 1 E 1 were the most active SULT forms. UGT 1 A 3, 1 A 4, and 1 A 6 as well as SULT 1 A 3 and 2 A 1 were of minor importance for the conjugation of XN. Three mono-glucuronides as well as three mono-sulfates were identified. Considering the tissue distribution of the tested UGT and SULT enzyme forms, these findings suggest a prominent role for the glucuronidation and sulfation of XN in the liver as well as in the gastrointestinal tract.     

Metabolism of the Hepatotoxic Compound Sophoraflavanone G in Rat Liver Microsomes

Our study aimed at investigating the metabolic characteristics of sophoraflavanone G (SFG), one of the hepatotoxic constituents of Sophora flavescens, in rat liver microsomes (RLMs). SFG was metabolized to 3 phase I metabolites, di‐hydroxylated SFG (M1), mono‐hydroxylated SFG (M2), dehydrogenated product of mono‐hydroxylated SFG (M3) and 3 SFG glucuronides (M4, M5, and M6) by RLMs. The formation kinetics of M2 conformed to biphasic kinetics in RLMs. The formation kinetics of M4 and M5 best‐fitted the Hill equation kinetics. Chemical inhibition studies found that CYP1A2 and CYP2E1 were the major enzymes responsible for the formation of M2, and the formation of M4 and M5 may be catalyzed by multiple UGT1A isoforms.     

The C‐glycosyl flavonoid,aspalathin, is absorbed,methylated and glucuronidated intact in humans

Human bioavailability of the flavonoid dihydrochalcones is little understood, and no evidence exists for C‐glycosyl flavonoid absorption in humans. The present study uses catechol‐O‐methyltransferase to generate methylated metabolites of aspalathin (a C‐glycosyl dihydrochalcone from rooibos tea). One of the methylated forms, both with and without glucuronidation, was detected using LC‐MS/MS in the urine of human subjects (n = 6), demonstrating that deglycosylation is not a prerequisite for C‐glycosyl flavonoid absorption. Methylation is catalysed by both intestine and liver cytosolic extracts. The results show that flavonoid C‐glycosides are methylated and glucuronidated in vivo in an intact form in humans.     

Structural characterization and antioxidant activities of 2 water-soluble polysaccharide fractions purified from tea (Camellia sinensis) flower

Abstract: The water‐soluble crude polysaccharide tea flower polysaccharide (TFP), obtained from tea (Camellia sinensis) flower by boiling‐water extraction and ethanol precipitation, was fractionated by Sephadex G‐100 column chromatography, giving 2 polysaccharide fractions termed TFP‐1 and TFP‐2. The structural features of TFP‐1 and TFP‐2 were investigated by high‐performance liquid chromatography (HPLC), gel‐permeation chromatography (GPC), rheometer, infrared (IR) spectra, nuclear magnetic resonance (NMR) spectroscopy, atomic force microscope (AFM), and scanning electron microscope (SEM). Results indicated that TFP‐1 was composed of glucose: xylose: rhamnose: galactose = 1.0:1.2:0.81:0.98 with a molecular weight of 167.5 KDa, while TFP‐2 comprised glucose: xylose: rhamnose: arabinose = 1.0:0.76:2.3:2.3 with a molecular weight of 10.1 KDa. The ¹H NMR revealed that TFP‐1 contained α‐L‐Rhap, α‐D‐Galp, α‐D‐GalpNAc, α‐D‐Xylp, α‐D‐Glcp, and β‐D‐Glcp residues, while TFP‐2 was illustrated to have α‐L‐Rhap, α‐L‐Arap, α‐D‐Xylp, α‐D‐Glcp, and α‐D‐GlcpNAc residues. Antioxidant activities of these fractions were investigated using various in vitro assay systems compared with ascorbic acid. In conclusion, TFP‐2 exhibited the higher antioxidant activities and could be explored as a novel potential antioxidant. Practical Application: At present, commonly low‐grade tea is preferred to extract the tea polysaccharide, to take full advantage of tea flower resource to extract polysaccharides can greatly reduce the cost of tea products. Thus, the search for plant‐derived biomaterials from this study could generate natural value‐added products from underutilized tea plant waste and used as a medicinal agent against chronic health problems, such as cancers, aging, and atherosclerosis caused by reactive free radicals that produced from oxidation.     

The influence of metabolism on the genotoxicity of catechol estrogens in three cultured cell lines

The 2- and 4-hydroxy metabolites of 17beta-estradiol (E2) and estrone (E1) are important for E2-mediated carcinogenesis due to the formation of genotoxic ortho-quinone metabolites. To assess the importance of metabolic conjugation for their genotoxicity, the DNA strand-breaking activity of the four catechol estrogens was determined in three cell lines with different activities of catechol-O-methyltransferase (COMT) and UDP-glucuronosyltransferase (UGT). Most DNA strand breaks were observed in V79 cells, which lack these metabolic activities. 2- and 4-hydroxy-E2 were 2.5 times more genotoxic than 2- and 4-hydroxy-E1. MCF-7 cells exhibit COMT activity, and the incidence of DNA strand breaks decreased with increasing methylation; only the 4-hydroxy metabolites of E1 and E2, which were poor substrates of COMT, exhibited low genotoxicity. HepG2 cells converted the catechol and methoxy metabolites of E2 to the respective E1 metabolites by 17beta-hydroxysteroid dehydrogenase (HSD). Moreover, methylation and glucuronidation took place. Only 4-hydroxy-E1 elicited a weak genotoxic response in these cells. The extensive metabolism in HepG2 cells is proposed to account for the failure of catechol estrogens to induce DNA strand breaks. Thus, metabolism by COMT and UGT and, to a minor extent, by HSD is a major determinant for the genotoxicity of catechol estrogens in target cells.     

INHIBITORY POTENTIAL OF WINE AND TEA AGAINST α-AMYLASE AND α-GLUCOSIDASE FOR MANAGEMENT OF HYPERGLYCEMIA LINKED TO TYPE 2 DIABETES

ABSTRACT

Natural α‐amylase and α‐glucosidase inhibitors from food‐grade plants offer an attractive strategy to manage postprandial hyperglycemia for type 2 diabetes management via control of starch breakdown and intestinal glucose absorption. In this study, four random sources of red and white wines as well as four types of teas were investigated for α‐amylase and α‐glucosidase inhibitory potential. Water extracts of black tea had the highest α‐glucosidase inhibitory activity, followed by white tea and oolong tea. All the randomly selected red wines had significant α‐glucosidase inhibitory activity compared to white wine. The α‐glucosidase inhibitory activity of the tea and wines correlated to the phenolic content, antioxidant activity and phenolic profile of the extracts. Further, these extracts had less or no α‐amylase inhibitory activity, indicating potential to overcome the side effects of undigested starch. This research has relevance for managing hyperglycemia and related oxidation‐linked dysfunction and concurrently reducing problems of undigested starch.

PRACTICAL APPLICATIONS

In this study anti‐diabetic‐relevant potential of wines and teas were confirmed in four types of red and white wines as well as four types of commonly available teas using in vitro enzyme assays for alpha‐glucosidase and alpha‐amylase inhibitory activities. In vitro inhibitory activities of these enzymes provide a strong biochemical rationale for further in vivo studies and dietary management strategy for type 2 diabetes through the control of glucose absorption. Further this phenolic antioxidant‐enriched dietary strategy using specific beverage combinations can generate a whole food profile that has the potential to reduce hyperglycemia‐induced pathogenesis and also associated complications linked to cellular oxidation stress.     

Screening grape seeds recovered from winemaking by‐products as sources of reducing agents and mammalian α‐glucosidase and α‐amylase inhibitors

Grape seeds collected from vinification of various grape varieties were extracted by supercritical CO₂ for oil recovery. The defatted residues thus obtained were considered as a re‐utilisable co‐product and assessed for phenolic content, reducing capacity and inhibitory activities against mammalian α‐amylase and α‐glucosidase enzymes. Supercritical CO₂ treatment led to higher recovery of anthocyanins. Reducing capacity of phenolic extracts reached up to ~2200 mmolFe(II) kg^?1, much higher than that of various natural phenolic sources. The anthocyanin‐rich extracts showed the highest inhibitory effectiveness towards α‐glucosidase (I₅₀ value equal to ~40 μg gallic acid equivalents (GAE)/mL ~ half than acarbose). Inhibitory effectiveness towards α‐amylase activity was similar among grape varieties, with I₅₀ values comparable to that of acarbose and correlated with proanthocyanidin contents. These results could pave the way for an efficient processing of grapes, including cascade processes, namely: winemaking, oil extraction from recovered grape seeds and phenolic extraction from defatted grape seeds as potential cost‐effective nutraceuticals.     

Flavonoids quercetin,myricetin, kaemferol and (+)‐catechin as antioxidants in methyl linoleate

The antioxidant effect of the flavonoids quercetin, myricetin, kaemferol, (+)‐catechin and rutin on methyl linoleate oxidation was investigated. In addition, the synergistic effects of flavonoids and α‐tocopherol were studied. Oxidation was monitored by conjugated diene measurement and by determining the formation of hydroperoxide isomers by HPLC. The antioxidant activity of flavonoids in non‐polar methyl linoleate differ from that previously reported in water‐containing systems, such as LDL and liposome systems. The activity of antioxidants (10–1000 μM ) measured by hydroperoxide formation decreased in the order: myricetin>quercetin>α‐tocopherol>(+)‐catechin >kaemferol=rutin. The antioxidant activity of flavonoids increased as the number of phenolic hydroxyl groups increased. In addition to the number of hydroxyl groups, other structural features such as the 2,3 double bond in the C‐ring and a glycoside moiety in the molecule had an effect on the antioxidant activity. Myricetin and rutin, especially had a synergistic effect with α‐tocopherol. Myricetin, quercetin and rutin protected α‐tocopherol from decomposition, myricetin being the most protective. The relative hydrogen‐donating activity measured by the ratio of cis,trans‐ to trans,transhydroperoxide isomers formed during oxidation decreased in the order: α‐tocopherol >myricetin>quercetin. Hydroperoxide isomeric distribution of the samples containing kaemferol or rutin did not differ from the control. Thus, although α‐tocopherol was the most effective hydrogendonor, myricetin and quercetin were more effective antioxidants in inhibiting the hydroperoxide formation in methyl linoleate. © 1999 Society of Chemical Industry     

Aerobic and anaerobic in vitro testing of feed additives claiming to detoxify deoxynivalenol and zearalenone

Deoxynivalenol (DON) and zearalenone (ZEN) are mycotoxins produced by fungi of the genus Fusarium which frequently contaminate maize and grain cereals. Mycotoxin-contaminated feed endangers animal health and leads to economic losses in animal production. Several mycotoxin elimination strategies, including the use of commercially available DON and ZEN detoxifying agents, have been developed. However, frequently there is no scientific proof of the efficacy of such adsorbents and degrading products. We therefore tested 20 commercially available products claiming to detoxify DON and/or ZEN either by biodegradation (4 products) or a combination of degradation and adsorption (16 products) under aerobic and anaerobic conditions at approx. pH 7. Under the applied conditions, a complete reduction of DON and consequent formation of the known non-toxic metabolite DOM-1 was exclusively observed in samples taken from the anaerobic degradation experiment of one product. For all other products, incubated under aerobic and anaerobic conditions, a maximum DON reduction of 17% after 72 h of incubation was detected. Aerobic and anaerobic incubation of only one tested product resulted in complete ZEN reduction as well as in the formation of the less-toxic metabolites DHZEN and HZEN. With this product, 68–97% of the toxin was metabolised within 3 h. After 24 h, a ZEN reduction ≥ 60% was obtained with four additional products during aerobic incubation only. Six of the 20 investigated products produced α- and/or β-ZEL, which are metabolites showing similar oestrogenic activity compared to ZEN. Aerobic and anaerobic degradation to unknown metabolites with unidentified toxicity was obtained with 10 and 3 products, respectively. The results of our study demonstrate the importance of in vitro experiments to critically screen agents claiming mycotoxin detoxification.     

Anthocyanin-derived phenolic acids form glucuronides following simulated gastrointestinal digestion and microsomal glucuronidation

Scope: Current research indicates that anthocyanins are primarily degraded to form phenolic acid products. However, no studies have yet demonstrated the metabolic conjugation of these anthocyanin‐derived phenolic acids in humans. Methods and results: Within the present study, a simulated gastrointestinal digestion model was used to evaluate the potential degradation of anthocyanins post‐consumption. Subsequently, cyanidin (Cy) and pelargonidin and their degradation products, protocatechuic acid and 4‐hydroxybenzoic acid, were incubated in the presence of human liver microsomes to assess their potential to form hepatic glucuronide conjugates. For structural conformation, phenolic glucuronides were chemically synthesised and compared to the microsomal metabolites. During the simulated gastric digestion, anthocyanin glycosides (200 μM) remained stable however their aglycone derivatives were significantly degraded (20% loss), while during subsequent pancreatic/intestinal digestion only pelargonidin‐3‐glucoside remained stable while cyanidin‐3‐glucoside (30% loss) and Cy and pelagonidin aglycones were significantly degraded (100% loss, respectively). Following microsomal metabolism, pelargonidin formed 4‐hydroxybenzoic acid, which was further metabolised (65%) to form two additional glucuronide conjugates, while Cy formed protocatechuic acid, which was further metabolised (43%) to form three glucuronide conjugates. Conclusions: We propose that following ingestion, anthocyanins may be found in the systemic circulation as free or conjugated phenolic acids, which should be a focus of future dietary interventions.     

Interaction of aqueous extracts of two varieties of Yam tubers (Dioscorea spp) on some key enzymes linked to type 2 Diabetes in vitro

This study sought to assess the effect of processing of yam flour [from white yam (Dioscorea rotundata) and water yam (Dioscorea alata)] to paste, on the antioxidant properties and inhibition of key enzymes linked to type‐2 diabetes (α‐amylase and α‐glucosidase). The phenolic content (phenol and flavonoid), antioxidant properties, α‐amylase and α‐glucosidase inhibitory properties of the aqueous extracts of the yam products were determined. Processing into paste caused significant (P < 0.05) percentage decrease in their total phenol and flavonoid content of the yam varieties. However, significant increase (P < 0.05) in the antioxidant properties of the yam varieties was observed after processing. Furthermore, the yam extracts inhibited α‐amylase and α‐glucosidase activities in vitro in a dose‐dependent parttern (1–4 mg mL^?1), however, the pasting process caused significant (P < 0.05) decrease in the α‐amylase inhibitory and α‐glucosidase inhibitory activities. Therefore, processing the yam varieties into paste (browned) could potentially increase their antioxidant capacity as well as decreasing their α‐amylase and α‐glucosidase inhibitory properties.     

Molecular Weight Affected Antioxidant,Hypoglycemic and Hypotensive Activities of Cold Water Extract from Pleurotus citrinopileatus

Cold water extract of P. citrinopileatus (CWEPC) was fractioned into 4 fractions, PC‐I (<1 kDa), PC‐II (1‐3.5 kDa), PC‐III (3.5‐10 kDa), and PC‐IV (>10 kDa), by ultrafiltration. The antioxidant activities, the inhibition of pancreatic α‐amylase, intestinal α‐glucosidase, and hypertension‐linked angiotensin converting enzyme (ACE), as well as the contents of polysaccharides, protein, and phenolic compounds of 4 fractions were determined. The results showed that lower MW fractions exerted a higher antioxidant activity, which was correlated to phenolic contents. The high molecular fraction (PC‐IV) exhibited significantly higher inhibitory activity on α‐amylase, α‐glucosidase, and ACE compared to CWEPC and the other 3 lower MW fractions (<10 kDa), which was more related to protein contents. The inhibition capability of CWEPC and PC‐IV on α‐amylase activity was 1/13.4 to 1/2.7 relative to that of acarbose, respectively. Kinetic data revealed that PC‐IV fraction followed a noncompetitive inhibition pattern on α‐glucosidase activity. The study demonstrated that various MW fractions and types of components contribute to different biological functions of P. citrinopileatus and it is protein constituents but not peptides responsible for the hypoglycemic potential of CWEPC.     

Content of Individual Phenolic Acids in Worts and Beers and their Possible Contribution to the Antiradical Activity of Beer

Phenolic acids are widely distributed in foods and raw materials. They are easily absorbed by humans due to their simplicity. Once they enter the blood plasma, they act as antioxidants. Beer can be a rich source of phenolic acids in the diet. The aim of this study was to determine the concentrations of phenolic acids in two experimental worts and beers as well as in nine market beers (using HPLC‐UV). An examination of the total antiradical activities of phenolic acids with in vitro model systems (using ABTS and DPPH free radicals), at the concentrations comparable to those detected in beers, was performed. Only low fractions of the main phenolic acids present in barley malt (ferulic, vanillic and p‐coumaric acid) were detected in the experimental worts. Moreover, the concentrations of phenolic acids significantly decreased until the last steps of beer production. The main beer phenolic acids (vanillic and ferulic acid) exerted a lower share of total antiradical activity against both free radicals (calculated as the sum of the individual activities of all acids detected in beer) than the minor phenolic acids (caffeic, chlorogenic, o‐coumaric, sinapic or syringic acid). The synergies, between individual phenolic acids in pairs, were also studied with in vitro model solutions using free radicals. The total antiradical activity of the compounds studied in pairs, was at the most as high as the sum of the antiradical activity of the individual phenolic acids, but in most cases it was considerably lower (i.e. no synergy was detected).     

Effects of germination on the activities of amylases and phenolic enzymes in sorghum varieties grouped according to food end‐use properties

Fifty sorghum varieties were screened to determine the effects of germination on levels of starch, α‐amylase, β‐amylase, phenylalanine ammonia lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO). Germination decreased starch content, with amylose being more degraded than amylopectin. In germinated grain, α‐amylase activity increased several‐fold in all varieties, whereas β‐amylase activity did not increase uniformly and even decreased in some varieties. Activity of the key enzyme in phenolic biosynthesis, PAL, was detected in only half of the varieties before germination but in all of them after germination. PPO was not activated in germinated sorghum grains, whereas POX activity increased up to tenfold in some varieties. Zymography revealed that germination induced de novo synthesis of several POX isoenzymes, among which an anionic POX isoenzyme (pI 3.1) was ubiquitously present. Amylase and phenolic enzyme activities could be correlated with grain and plant agronomic characteristics. The use of sorghum varieties for local dishes such as ‘tô’, ‘dolo’, couscous and thin porridge could be correlated with amylase and phenolic enzyme activities and the contents of their substrates. The biochemical constituents determined are useful markers for selection of varieties for food utilisation with special emphasis on infant porridges. Copyright © 2006 Society of Chemical Industry