Phenolic constituents of Porophyllum obscurum

Porophyllum Genus Compounds and Pharmacological Activities: A Review

The genus Porophyllum (family Asteraceae) is native to the western hemisphere, growing in tropical and subtropical North and South America. Mexico is an important center of diversification of the genus. Plants belong of genus Porophyllum have been used in Mexican traditional medicine to treat kidney and intestinal diseases, parasitic, bacterial, and fungal infections and anti-inflammatory and anti-nociceptive activities. In this sense, several trials have been made on its chemical and in vitro and in vivo pharmacological activities. These studies were carried on the extracts and isolated compounds and support most of their reported uses in folk medicine as antifungal, antileishmanial, anti-inflammatory, anti-nociceptive and burn repair activities, and as a potential source of new class of insecticides. Bio guided phytochemical studies showed the isolation of thiophenes, terpenes and phenolics compounds, which could be responsible for the pharmacological activities. However, more pre-clinical assays that highlight the mechanisms of action of the compounds involved in pharmacological function are lacking. This review discusses the current knowledge of their chemistry, in vitro and in vivo pharmacological activities carried out on the plants belonging to the Porophyllum genus.

Antifungal photosensitive activity of Porophyllum obscurum (Spreng.) DC.: Correlation of the chemical composition of the hexane extract with the bioactivity

We report Porophyllum obscurum as a source of new photosensitizers with potential use in Photodynamic Therapy as an alternative for oropharyngeal candidiasis treatment. The antifungal photosensitive activity of different extracts from P. obscurum was evaluated by using microdilution and bioautographic assays. The Minimum Fungicidal Concentration for hexanic extract under UV-A irradiation was 0.98μg/mL, but it was inactive in experiments without irradiation. The bioassay-guided fractionation of this extract led to the isolation of four thiophenes responsible for the photosensitive activity: 2,2':5'2″terthiophene, 5-(3-buten-1-ynyl)-2,2'-bithiophene, 5-(4-acetoxy-1-butenyl)-2,2'- bithiophene and 5-(4-hydroxy-1-butenyl)-2,2'- bithiophene, with Minimum Fungicidal Concentrations ranging 0.24-7.81μg/mL under UV-A irradiation. The activity of the hexanic extract was evaluated against 25 clinical strains of Candida spp. isolates as etiological agents of oropharyngeal candidiasis. No differences in susceptibility were observed in strains resistant and susceptible to conventional antifungal drugs. Qualitative and quantitative chemical analyses of seven samples of P. obscurum collected in four different phenological stages were carried out showing that full flowering stage possesses the highest thiophenes content. These data also allowed us to establish a correlation between the thiophene composition of the different extracts and their antifungal photosensitive activity, according to a second order polynomial model with the equation: y=11.2603-0.6831*x+0.0108*x². The thiophenes isolated were the responsible of antifungal photosensitive activity and can be used for the future standardization of the extract. Results showed that P. obscurum hexanic extract could be potentially developed as an Herbal Medicinal Product to be applied as a photosensitizer in Photodynamic Therapy.