ABSTRACT
Taxifolin has a plethora of therapeutic activities and is currently isolated from the stem bark of the tree Larix gmelinni(Dahurian larch).It is a flavonoid of high commercial interest for its use in supplements or in antioxidant-rich functional foods.However,its poor stability and low bioavailability hinder the use of flavonoid in nutritional or pharmaceutical formulations.In this work,taxifolin isolated from the seeds of Mimusops balata,was evaluated by in silico stability prediction studies and in vitro forced degradation studies(acid and alkaline hydrolysis,oxidation,visible/UV radiation,dry/humid heating)monitored by high performance liquid chromatography with ultraviolet detection(HPLC-UV)and ultrahigh perfor-mance liquid chromatography-electrospray ionization-mass spectrometry(UPLC-ESI-MS).The in silico stability prediction studies indicated the most susceptible regions in the molecule to nucleophilic and electrophilic attacks,as well as the sites susceptible to oxidation.The in vitro forced degradation tests were in agreement with the in silico stability prediction,indicating that taxifolin is extremely unstable(class 1)under alkaline hydrolysis.In addition,taxifolin thermal degradation was increased by humidity.On the other hand,with respect to photosensitivity,taxifolin can be classified as class 4(stable).Moreover,the alkaline degradation products were characterized by UPLC-ESI-MS/MS as dimers of taxifolin.These results enabled an understanding of the intrinsic lability of taxifolin,contributing to the development of stability-indicating methods,and of appropriate drug release systems,with the aims of preserving its stability and improving its bioavailability.
ABSTRACT
Abstract Solvents play important and critical role in natural product chemistry and could generate artefacts during the extraction and purification of metabolites from a biological matrix. This study aimed to correlate the chromatographic profile with biological activity of Ipomoea pes-caprae (L.) R. Br., Convolvulaceae, extracts obtained with hydroethanolic extraction. Thus, aerial parts of I. pes-caprae were extracted with different concentration of ethanol (50, 70 and 90°GL) and the obtained extracts were analysed by HPLC-UV. HPLC data were studied employing chemometrics to discriminate the samples. Moreover these samples were further characterized by using UPLC-QTOF/MS data. The extracts were also biomonitored through the paw-oedema and spontaneous nociception induced by trypsin in mice. Different chromatographic profiles were obtained and the exploratory analysis clearly revealed higher level of ethyl caffeate in extracts of lower strength of ethanol (50°GL). This compound was suggested to be an artefact formed by transesterification of caffeoylquinic acid derivatives present in the plant, once it was not observed when other solvents were employed. During the biological assay, only the extract obtained with ethanol 50°GL presented significant inhibition of inflammation (45 ± 9%) and nociception (24 ± 3%). Ethyl caffeate seems to be linked to the anti-inflammatory effect since it reduced 86 ± 5% of paw-oedema induced by trypsin. Artefacts could contribute to the biological activity of herbal preparations and consequently lead to misinterpretation of the results.