The antioxidant and pro-oxidant effects of thymoquinone (TQ), a natural main constituent of the volatile oil of Nigella saliva seeds, and a synthetic structurally-related tert-butylhydroquinone (TBHQ), were examined in vitro. Both TQ and TBHQ efficiently inhibited iron-dependent microsomal lipid peroxidation in a concentration-dependent manner with median inhibitory concentration (IC50) values of 16.8 and 14.9 microM, respectively. TBHQ was stronger than TQ as a scavenger of 2,2'-diphenyl-p-picrylhydrazyl radical (DPPH) (IC50 = 5 microM, 200 times more active than TQ) and as a scavenger of hydroxyl radical (OH*) with an IC50 of 4.6 microM (approximately 10 times more active than TQ). TQ was more active than TBHQ as a superoxide anion scavenger with IC50 of 3.35 microM compared to 18.1 microM for TBHQ. Only TBHQ significantly promoted DNA damage in the bleomycin-Fe(III) system. The results suggest that both TQ and TBHQ have strong antioxidant potentials through scavenging ability of different free radicals. Moreover, the data indicate that TQ is acting mainly as a potent superoxide anion scavenger.

Extraordinary actions have been implemented in an effort to control the rapid spread of the ongoing COVID-19 epidemic in Egypt. People's adherence to control measures is influenced by their knowledge, attitudes and practices towards the disease. Therefore, in the present study we assessed pharmacy senior students' knowledge, attitudes and practices towards the COVID-19 pandemic. An online questionnaire was created and it consisted of 12 questions testing their knowledge about COVID-19 clinical characteristics, transmission routes and prevention and control steps. Among senior pharmacy students (n = 238), 70% were females and 63% were living in greater Cairo. Their main source of information included social media (70%), published articles (48%) and television (48%). The overall correct knowledge score was 83%. Most of the students displayed a good COVID-19 knowledge level (72.5% of the students). The students were least informed when trying to answer questions about hyper-coagulation, as a major cause for death in patients with severe COVID-19, and about the timings on the necessity to wear masks. Assessment of students' attitudes and practices towards COVID-19 reflected that 87% of them were confident that health care teams and scientists could win the fight against the virus. In addition, 72% of students agreed that COVID-19 will be controlled successfully. The greater the students' knowledge, the more confident they felt that COVID-19 will be controlled successfully (OR 2.2, 95% confidence interval [CI] 1.03-4.72). Good behavioral practice towards COVID-19 control was confirmed when 87% of students answered that they didn't go out to any crowded place. Females were 3.6 times (95% confidence interval [CI] 1.03-3.11) more likely to avoid going out than males. Bad behavioral practice became evident when approximately 50% of students admitted that they did not wear masks when they left their house. Therefore, more efforts should be taken to protect future pharmacists from this pandemic.

Thymoquinone (TQ) is the major active component of the volatile oil of Nigella sativa seeds. The effects of TQ on carbon tetrachloride (CC14)‐induced hepatotoxicity was investigated in male Swiss albino mice. Carbon tetrachloride (20 μl/Kg, i.p.) injected into mice, induced damage to liver cells and was followed by the increase in serum alanine aminotransferase (ALT) activity after 24 h. Oral administration of TQ in a single dose (100 mg/Kg) resulted in significant (p<0.001) protection against the hepatotoxic effects of CCl4. TQ was tested as a substrate for mice hepatic DT‐diaphorase in the presence of NADH. TQ appears to undergo reduction to dihydrothymoquinone (DHTQ). Reduction rates as a function of protein (liver homogenate) and substrate (TQ) concentrations are reported. An apparent Km of 0.1 mM and an apparent Vmax of 74 μmol/min/g liver were measured. TQ and DHTQ inhibited the in vitro non‐enzymatic lipid peroxidation in liver homogenate (induced by Fe3+‐ascorbate) in a dose dependent manner. In this in vitro model DHTQ was more potent in comparison with TQ and butylated hydroxytoluene (BHT). The IC50 for DHTQ, TQ and BHT were found to be 0.34, 0.87 and 0.58 μM respectively. The data suggest that the in vivo protective action of TQ against CCl4‐induced hepatotoxicity may be mediated through the combined antioxidant properties of TQ and its metabolite DHTQ.

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The effects of thymoquinone (TQ) on cisplatin-induced nephrotoxicity in mice and rats were studied. Oral administration of TQ (50 mg/L in drinking water) for 5 days before and 5 days after single injections of cisplatin (5 mg/kg, i.v., in rats and 7 or 14 mg/kg, i.p., in mice) greatly ameliorated cisplatin-induced nephrotoxicity in both species. In rats, i.v. cisplatin caused 4- and 5-fold elevations in serum urea and creatinine, a 235% increase in urine volume, a 41% increase in kidney weight, 8.5-fold decrease in creatinine clearance, and extensive histological damage 5 days after treatment. In mice, similar alterations in kidney function were observed. TQ-induced amelioration of cisplatin nephrotoxicity was evident by significant reductions in serum urea and creatinine and significant improvement in polyuria, kidney weight, and creatinine clearance. The protective effects of TQ against cisplatin-induced nephrotoxicity in the rat were further confirmed by histopathological examination. To evaluate the possible modification of the antitumor activity of cisplatin by TQ, we studied their interaction in Ehrlich ascites carcinoma (EAC) bearing mice. The results revealed that TQ potentiated the antitumor activity of cisplatin. The current study suggests that TQ may improve the therapeutic index of cisplatin.

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