Modelling of Protein-Polyphenol Interactions

Prof. Stephen R. Euston, Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, Scotland.

The interaction between proteins and polyphenols is known to modify both the bioavailability and bioactivity of dietary polyphenols. Understanding these interactions can facilitate the design of delivery systems for polyphenols in the digestive tract. Molecular modelling of protein-polyphenol and protein-ligand interactions in general has long been used as a way to identify mall mole ule biding sites on proteins. However, these are often used without a careful consideration of the assumptions used and limitations of these methods, and how this affects the accuracy of the predictions. In this talk, two common methods for predicting binding site location and binding energy, molecular dynamics simulation and molecular docking, will be discussed. The simplifications and assumptions implicit in these approaches, as well as ways to improve their predictions will be covered.

Fagara zanthoxyloides is a medicinal plant used in traditional medicine for the treatment of elephantiasis, toothache, sexual impotence, malaria, dysmenorrheal and abdominal pain among rural dwellers. The aim of the present study was to evaluate the in vivo and in vitro anti-inflammatory effect of the methanol extracts of the leaves of Fagara zanthoxyloides to validate its use in folklore medicine. The analysis of the phytochemical content of the leaf extract of Fagara zanthoxliodes revealed the presence of different secondary metabolites (tannins, saponin, terpenoids, steroids, flavonoids, alkaloids, phenols and glycoside) in varying proportions. In the systemic oedema of the rat paw, scalar doses (50, 100 and 250 mg/kg b.w) of the extract significantly (p < 0.05) suppressed the development of paw oedema induced by egg albumin at different time intervals (0.5 hr- 5 hrs). This compares well with a standard anti–inflammatory drug indomethacin (10 mg/kg b.w). Varying doses of the extract (1.0, 1.2, 1.4, 1.6 and 1.8 ml) significantly (p< 0.05) inhibited phospholipase A₂ activity in a concentration-related manner provoking inhibition comparable to that of prednisolone, a standard anti-inflammatory drug. Similarly, the extract significantly (p< 0.05) inhibited CaCl₂-Induced platelet aggregation in a dose and time dependent manner. The extract also significantly (p< 0.05) inhibited hypotonicity induced membrane stabilization. These results indicate that the extract produced potential anti-inflammatory activity which could be as a result of the rich phytochemical constituents.

Aims: Therapeutic and/or preventive interventions using phytochemical constituents for ischemic heart disease have gained considerable attention worldwide, mainly due to its antioxidant activity. This study investigated the cardioprotective effect and possible mechanism of juglone, a major constituent of Walnut tree, using isoproterenol (ISO)-induced myocardial infarction (MI) model in rats.

Methodology: Rats were pretreated for five (5) days with juglone (1, 3 mg/kg, i.p) and atenolol (1 mg/kg, i.p) in separate experiments before inducing myocardial injury by the administration of ISO (80 mg/kg, s.c) at an interval of 24 hrs for 2 consecutive days (4^th and 5^th day). The cardioprotective effect of juglone was confirmed through lead II electrocardiograph (ECG), the cardiac biomarkers (ALT, AST, CPK, CK-MB, LDH and cTnI) and histopathological study.

Results: The results of our present study suggest that prior administration of juglone proved to be effective as a cardioprotective therapeutic agent in reducing the extent of myocardial damage (induced by ISO) by fortifying the myocardial cell membrane, heart tissue architecture, preventing inflammation, edema, necrosis and also by normalizing cardiac marker enzymes (AST, ALT, CPK, CK-MB, LDH and cTnI). Conclusion: In conclusion, this study has identified phytochemical constituents: juglone as a potential cardioprotective agent.

The existence of oxidative stress in the pathogenesis of benign prostatic hyperplasia (BPH), characterized by elevation in markers of oxidative stress/lipid peroxidation (8-hydroxyguanosine, malondialdehyde and 8-hydroxynonenal) and reduction in antioxidant status (catalase, superoxide dismutase, glutathione peroxidase and reduced glutathione) is scientifically documented. We hypothesize that a good treatment regimen for BPH should return the pro-oxidant/antioxidant status to normal; hence, pro-oxidant/antioxidant status is an indirect indicator of treatment response. In this study, the effect of crude methanol extract (CME) of Zapoteca portoricensis root and its methanol (MF) and ethyl acetate (EAF) fractions on the pro-oxidant/antioxidant status of experimentally-induced BPH was investigated. Forty-five Wistar albino rats (7 weeks, 180-200 g) used in this study were divided into nine groups (n = 5). Group 1 served as normal control. BPH was induced in groups 2-9 by daily subcutaneous administration of dihydrotestosterone (400 μg/ml) and estradiol (80 μg/ml) for 28 days. Group 2 served as BPH-control (was left untreated) while group 3 received dutesteride (Avodart®). Groups 4 and 5, 6 and 7, and 8 and 9 received, by gavage 200 and 400 mg/kg/d b.w. of CME, 200 and 400 mg/kg/d b.w. of MF, and 200 and 400 mg/kg/d b.w. of EAF, respectively for 14 days. There were increased prostatic specific (PSA) and malondialdehyde but reduced antioxidant status in BPH-control relative to normal control. At 400 mg/kg/d b.w, CME, MF and EAF decreased prostatic specific antigen by 55.91%, 57.54% and 56.75%, respectively comparable to 58.80% by dutesteride. In addition, the results of histological assessment of prostate tissues of the experimental rats fed extracts demonstrate an improved prostate status. The extracts returned the pro-oxidant/antioxidant status modified by BPH to normal. These findings may justify the plant’s folkloric use and suggest that extracts can be exploited further as potential source of entities for managing BPH.