The novel coronavirus of 2019 (nCoV-19) has become a pandemic, affecting over 205 nations with over 7,410,000 confirmed cases which has resulted to over 418,000 deaths worldwide. This study aimed to identify potential therapeutic compounds and phytochemicals of medicinal plants that have potential to modulate the expression network of genes that are involve in SARS-CoV-2 pathology in human host and to understand the dynamics key proteins involved in the virus-host interactions. The method used include gene network analysis, molecular docking, and sequence and structure dynamics simulations. The results identified DNA-dependent protein kinase (DNA-PK) and Protein kinase CK2 as key players in SARS-CoV-2 lifecycle. Among the predicted drugs compounds, clemizole, monorden, spironolactone and tanespimycin showed high binding energies; among the studied repurposing compounds, remdesivir, simeprevir and valinomycin showed high binding energies; among the predicted acidic compounds, acetylursolic acid and hardwickiic acid gave high binding energies; while among the studied anthraquinones and glycosides compounds, ellagitannin and friedelanone showed high binding energies against 3-Chymotrypsin-like protease (3CL pro), Papain-like protease (PL pro), helicase (nsp13), RNA-dependent RNA polymerase (nsp12), 2'-O-ribose methyltransferase (nsp16) of SARS-CoV-2 and DNA-PK and CK2alpha in human. The order of affinity for CoV proteins is 5Y3E > 6NUS > 6JYT > 2XYR > 3VB6. Finally, medicinal plants with phytochemicals such as caffeine, ellagic acid, quercetin and their derivatives could possibly remediate COVID-19.

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Melanin is s most widely distributed pigment and is found in bacteria, fungi, plants, and animals. Melanogenesis is under complex regulatory control by multiple agents interacting through pathways activated by hormonal and receptor-dependent and -independent mechanisms. There are about 20 genes that are involved in the biochemical pathway of melanogenesis and its regulation, which include: tyrosinase, microphthalmia-associated transcription factor, melanocortin1 receptor, adenylate cyclase, protein kinase A. Human melanogenesis regulatory proteins such as MAPK1, CREB3, and CREBP, have binary interaction with the protein of herpesvirus, hepatitis C virus, Human immunodeficiency virus type 1, Simian virus 40, and Human adenovirus A and C. Melanin is a double-edged sword in host-pathogen interaction (e.g., human-bacteria and/or fungi interaction). The inducers of upregulation of melanogenesis include fluvoxamine, famotidine, terbutaline, heliotrine, sirolimus, dicoumarol, Prestwick-860, carbimazole, (-)-MK-801, rilmenidine, hydrastine hydrochloride, haloperidol, scopolamine N-oxide, raubasine, and dihydroergocristine. In melanogenesis, GSK3B, CSNK2A, MAPK1, MAPK3, MAPK14, ERK1, and HIPK2 were the major kinases, while RUNX1, GATA1, and REST, SUN12, and RCOR1 were the major transcription factors. This study has reviewed the melanogenesis pathway, its regulations as well as applications to viral infection. The antiviral activity of melanin and its complex in the presence of antibacterial and antifungal compounds should be investigated to further provide insight for biomedical, biotechnological, and pharmacological applications.

Introduction: Irvingia gabonensis belongs to the Irvingiaceae plant family and commonly known as the African bush mango, wild mango, Dika nut and Manguier sauvage. The fruits of I. gabonensis are edible and their use in traditional medicine has been reported for the treatment of diabetes, diarrhea, wound ulcer, hepatic disorder, microbial infections, and inflammatory pains.  Aim: This study aimed to identify the standard phenolic contents of I. gabonensis fruit pulp and peel extracts and investigate the bind energy on polyphenol oxidase in order to know why browning of I. gabonensis fruit is often rapidly occur and how to prevent it with suitable inhibitor in an industrial processing. Results: The phenolics that were identified include ellagic acid, cinnamic acid, gallic acid, 3-friedelanone, lupeol, kaempferol, quercetin, alpha-curcumene and zingiberene. The two PPO from Solanum lycopersicum (PDB ID: 6HQI) and Mangifera indica (PDB: D2XZ13_model) have different binding energies across the ligands with highest score by 3-friedelanone (-14.3 and -16.1 kcal/mol respectively), followed by lupeol (-13.9 and -14.6 kcal/mol respectively). The differences in the binding energies across the plant PPOs could be due to variation in the amino acid composition and more importantly the amino acid residues that participate in the catalytic and allosteric activities Conclusion: This study has shown the reason behind rapid browning that usually occur in I. gabonensis and more importantly, the need for effective edible inhibitors of PPO.

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This paper focuses on the evaluation of nutritional and anti-nutritional potentials, antioxidant, and phenolic constituents of edible portions (peel and pulp) of African bush mango (Irvingia gabonensis) fruit. The nutritional status of I. gabonensis fruit peel and pulp were evaluated by determining the proximate indices, vitamin (A and C), mineral compositions and antioxidant analyses. All these were quantified using standard methods. The results of the proximate analysis showed moisture content (79.4 - 81.33 g/100g), mineral ash (0.59 - 0.87 g/100g), crude fibre (9.32 - 10.27 g/100g), crude protein (1.22 - 1.57 g/100g), crude fat (1.69 - 2.23 g/100g) and carbohydrate (5.78 - 5.98 g/100g) per fresh weights respectively. Among all minerals, potassium was found to have highest values with 31.3 ± 0.62 mg/100g and 29.5 ± 0.78 mg/100g for the peel and pulp respectively. The pulp and peel of I. gabonesis showed almost similar pattern of scavenging activities while the pulp showed higher total antioxidant capacity than peel. Tannin and oxalate contents are lower in the pulp than peel, while the phytate and the alkaloid contents are higher in the pulp extract than peel. HPLC analysis confirmed the predominant compounds which include,  ellagic acid (121 mg/100g); protocatechuic acid (65 mg/100g);  gallic acid (46.2 mg/100g); chlorogenic acid (37.9 mg/100g); caffeic acid (9.33 mg/100g); and kaempferol (3.05 mg/100 g) for the peel extract while pulp gave ellagic acid (0.071 mg/100g); protocatechuic acid (1.65 mg/100g);  gallic acid (3.73 mg/100g);  chlorogenic acid (3.56 mg/100g); caffeic acid (0.85 mg/100g); and kaempferol (0.08 mg/100g).. The underutilized tropical fruit of I. gabonensis has considerable antioxidant activity and may possess phytochemicals that could impact human health.

Polyphenol oxidase (PPO) is an enzyme that is responsible for the enzymatic browning of fruits and vegetables. This is generally undesired process and need to be prevented in food technology. PPO from seeds of Citrullus colocynthis was purified, the physicochemical properties such as effects of pH and temperature, substrate specificity, effects of inhibitors and cations on PPO activity and the kinetic parameters for four substrates namely, catechol, L-DOPA, gallic acid and tyrosine, were determined. The purification steps resulted in 41-fold with 10 % yield, and the optima pH and temperature values for PPO from C. colocynthis were found to be pH 7.0 and 60 °C, respectively using catechol as substrate. About 9 % enzyme initial activity was retained after 60 min of incubation at 80 °C, and the apparent molecular weight was determined as 42 kDa by partially denaturing SDS-PAGE. PPO activity was inhibited by ascorbic acid, SDS and certain divalent (Ca2+, Zn2+, Mg2+ and, Fe2+) and monovalent (Na+) metal. Moreover, purified enzyme solution showed diphenolase activity toward catechol, gallic acid, L-DOPA and monophenolase activity toward tyrosine, therefore, tyrosinase was identified as the only one PPO in C. colocynthis seeds. This study revealed the use of temperature above 80 °C to inhibit PPO activity during processing and storage of melon seeds.