Asian Pacific Journal of Tropical Medicine

460-466

Authors: Ying-Hen Hsieh

Objective: To ascertain the role of imported cases and serotypes on dengue outbreaks in Taiwan which have been sporadic yet highly volatile during the past two decades, exhibiting record-breaking magnitude in recent years. Methods: Confirmed case and serotype data from Taiwan Centers for Disease Control during 1998-2017 were fully examined, with fitting of weekly and daily case data of each city/county to a mathematical model to pinpoint the waves of cases and their locations. Moreover, we quantify the timing of turning point and transmission potential of each wave and determine its circulating serotype, to ascertain any pattern or connection between the variations in circulating serotypes and the magnitude/transmissibility of outbreak. Results: While the number of imported case increased steadily during past two decades, the yearly number of indigenous cases fluctuated wildly. Moreover, while yearly percentages of serotypes for imported cases remains steady, that of indigenous cases does not exhibit any clear pattern. There was at least one wave of reported cases somewhere in Taiwan every year from 1998 to 2015, except in 2016-2017. The effective reproduction number R for all waves in all locations ranged from 1.14 to 2.87, with the exception of two Tainan waves, in 2010 (3.95) and 2015 (6.84). Four major outbreaks of over 2000 cases reveal circulation of one dominant serotype. Conclusions: Correlation between imported cases and indigenous outbreak prove to be difficult to ascertain, even with the availability of serotype data. However, although there had been occasional co-circulation of serotypes in one location, and for some years with different serotypes circulating in different locations, all major outbreaks of over 2 000 cases during the past two decades are due to circulation of mainly a single serotype, perhaps indicating greater transmission potential with one dominating serotype.

473-479

Authors: Umme Salma, Taous Khan, Abdul Jabbar Shah

Objective: To explore the antihypertensive effect of extracts from the leaves of Hedera helix (H. helix) on normotensive and hypertensive rats in-vivo followed by vasodilatory studies in-vitro. Methods: The crude methanolic extract was prepared and the activity directed fractionation was carried out. Spectrophotometric analysis of total phenolic and flavonoid content was also done. HPLC analysis was performed for the detection of hederacoside C. In-vivo blood pressure study was carried out in normotensive and high salt-induced hypertensive Sprague-Dawley rats. Isolated aortic tissues from rat and rabbit were used for in-vitro studies. The effects were recorded and analyzed through PowerLab data acquisition system. Results: Crude extract of H. helix (1-30 mg/kg) decreased blood pressure to greater extent in high salt-induced hypertensive rats in-vivo compared to the normotensive [Max. fall (58.59±0.02) mmHg vs. (67.53±3.07) mmHg]. The n-hexane, chloroform, ethyl acetate and aqueous fractions were also checked. These fractions were more effective in hypertensive rats. Aqueous fraction was more potent and n-hexane the least. In isolated rat aortic rings precontracted with phenylephrine, crude extract induced endothelium-dependent effect. The endothelium-dependent component of vasodilatory effect was ablated with L-NAME, and denudation of endothelium. The aqueous fraction was most potent vasodilator. In aortic rings from hypertensive rats, extract and fractions produced partial endothelium-independent effect which was not affected by pretreatment with L-NAME, indicating endothelium dysfunction in the hypertensive rats and suggesting additional vasodilatory mechanisms. In rabbit aorta, the extract and fractions also inhibited phenylephrine and high K+ -induced precontractions, and shifted Ca++ concentration-response curves. Conclusions: Our findings indicate that extract and fractions of H. helix are antihypertensive remedies, which is the outcome of vasodilatory effect. This vasodilatory effect is mediated through nitric oxide and Ca++ antagonism.

486-494

Authors: Nawanit Thanaseelungkoon, Jakaphun Julsrigival, Kulwadee Phannachet, Sunee Chansakaow

Objective: To determine the chemical composition, as well as the antioxidant, antityrosinase and antibacterial activities of essential oils obtained from some Apiaceous and Lamiaceous plants collected in Thailand. Methods: The essential oils of the specified spices and aromatic herbs were obtained by hydro-distillation, and their chemical constituents were analyzed by gas chromatography/mass spectrometry. Antioxidant assays were based on the scavenging effects of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) free radicals as well as the lipid oxidation inhibition of ß-carotene bleaching by linoleic acid. Tyrosinase enzyme inhibition was evaluated by the dopachrome method. Broth microdilution technique was performed for the purposes of studying microbial growth inhibition against the isolated bacterial strains. Results: The essential oils of Elsholtzia stachyodes, Coleus amboinicus (I) and Trachyspermum ammi presented a high degree of potency in DPPH, ABTS and ß-carotene bleaching assays. The Trachyspermum ammi oil, which mainly contained thymol (49.04%) and p-cymene (22.06%), proved to be the most effective in terms of antibacterial activity. The major compositions of Coleus amboinicus (I) were carvacrol (51.57%), y-terpinene (18.04%) and p-cymene (7.81%); while thymol (43.76%) and y-terpinene (24.61%) were identified as the major components of Elsholtzia stachyodes oil, with p-cymene (6.73%) being identified as a minor constituent. Moreover, Cuminum cyminum oil containing cuminaldehyde (49.07%) and Elsholtzia communis oil composed with geranial (44.74%) and neral (35.27%) as the major components displayed a specific ability for the inhibition of the mushroom tyrosinase enzyme. Conclusions: The results indicated that these bioactive essential oils obtained from indigenous herbs are of significant interest as alternative raw materials in food, cosmetic and medicinal products.