The Effect of Altitude on Phenolic, Antioxidant and Fatty Acid Compositions of Some Turkish Hazelnut (Coryllus avellana L.) Cultivars.

Turkey is the leading producer and exporter of hazelnuts, producing approximately 64% of global hazelnut production. This research investigated the effects of cultivars and altitude on the phenolic, antioxidant, and fatty acid compositions of five hazelnut cultivars grown at three different altitudes, 100 m, 350 m, and 800 m, in Ordu province, one of the territories that produce the most hazelnuts. The results showed that the cultivar and location significantly affected phenolic compounds, antioxidant activity, and fatty acid (FA) content. The lowest (2.30 mg/kg-Yagli) and highest (21.11 mg/kg-Kara) gallic acids were obtained at 100 m. The highest total phenolic content and antioxidant activity were found in the nuts grown at 350 m in the Kara and Palaz cultivars, at 100 m in the Yagli and Sivri cultivars, and at 800 m in the Çakildak cultivar. Oleic acid was the predominant FA in the cultivars and possessed a diverse trend according to the altitude and cultivar, ranging from 76.04% to 84.80%, increasing with altitude in all cultivars except Çakildak. Palmitic acid was the predominant saturated FA followed by stearic acid, which significantly varied according to the elevations. This study suggests that the responses of hazelnuts to altitude depend on the cultivar; hence, a proper approach to producing nuts containing more phenolic, fatty acids, and antioxidant activity includes choosing a suitable cultivar for a specific elevation.

A novel method for explaining the product inhibition mechanisms via molecular docking: inhibition studies for tyrosinase from Agaricus bisporus.

The present study aims to investigate the substrate (4-methyl catechol and catechol) specificity and inhibition mechanisms (l-ascorbic acid, citric acid, and l-cysteine) of the tyrosinase enzyme (TYR), which is held responsible for browning in foods and hyperpigmentation in the human skin, through kinetic and molecular docking studies. During the experimental studies, the diphenolase activities of TYR were determined, following which the inhibitory effects of the inhibitors upon the diphenolase activities of TYR. The inhibition types were determined as competitively for l-ascorbic acid and citric acid and noncompetitive for l-cysteine. The kinetic results showed that the substrate specificity was better for catechol while l-cysteine showed the best inhibition profile. As for the in silico studies, they also showed that catechol had a better affinity in line with the experimental results of this study, considering the interactions of the substrates with TYR's active site residues and their distance to CuB metal ion, which is an indicator of diphenolase activity. Besides, the inhibitory mechanisms of the inhibitor molecules were explained by the molecular modeling studies, considering the binding number of the inhibitors with the active site amino acid residues of TYR, the number and length of H bonds, negative binding energy values, and their distance to CuB metal ion. Based on our results, we suggest that the novel method used in this study to explain the inhibitory mechanism of l-cysteine may provide an affordable alternative to the expensive methods available for explaining the inhibitory mechanism of TYR and those of other enzymes. HighlightsThe best affinity for the tyrosinase enzyme occurred with catechol.l-Ascorbic acid, citric acid, l-cysteine inhibited the diphenolic activity of tyrosinase.In silico studies confirmed the best affinity shown by catechol.Product inhibition mechanism of l-cysteine explained by in silico for the first time.Communicated by Ramaswamy H. Sarma.

An Innovator Support Material for Tyrosinase Immobilization: Antimony-Doped Tin Oxide Thin Films (ATO-TF).

Tyrosinase (T3824, Sigma) enzymes were immobilized onto SnO2: Sb thin films (ATO-TF) which were synthesized in laboratory conditions by spray pyrolysis technique. Immobilization of tyrosinase onto SnO2: Sb thin film (ATO-TF) was confirmed by scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR). The optimum pH of the immobilized tyrosinase (tyrosinase-ATO-TF) was 6.0, and the optimum temperature was found to be 30 °C. In the presence of catechol substrate of immobilized enzymes, Km and Vmax values were determined as 0.34 mM and 312.5 U/cm2 min, respectively. The thermal stabilities of the immobilized tyrosinase at 4 °C and 30 °C were investigated for 20, 40, and 60 min. At these temperatures and time intervals, the immobilized tyrosinase was found to be highly stable. The pH stability of the immobilized tyrosinase enzymes was incubated for 24, 48, 72, and 96 h at 4 °C temperature. The enzyme activity was determined under optimum conditions, and the activity of the immobilized tyrosinase enzymes exhibited various values for the range of pH 3.0-8.0. The storage stability of the immobilized tyrosinase enzymes at 4 °C was investigated, and 45.72% of the initial activity was maintained at the end of the seventh day. Furthermore, the reusability of the immobilized tyrosinase enzymes has been examined. The immobilized tyrosinase enzymes can be used 3 times and survived their 50% of initial activity. The ATO-TF can be used as alternative support materials for the immobilization of tyrosinase enzymes.