Anti-inflammatory activity of Penstemon gentianoides and Penstemon campanulatus

Context: Penstemon gentianoides (Kunth) Poir. and Penstemon campanulatus (Cav.) Willd. (Plantaginaceae) are important medicinal plants in Mexico used by indigenous people for their anti-inflammatory effects and to also reduce rheumatic pains. Objective: In addition to radical scavenging activity, the anti-inflammatory activity of the extracts, fractions and compounds of these plants were investigated and reported here for the first time. Materials and methods: The anti-inflammatory activities of MeOH, CH2Cl2, and ethyl acetate extracts and iridoid, flavonoids, and phenylpropanoids from Penstemon gentianoides and P. campanulatus were studied in the TPA-induced mouse ear edema model. In addition, antioxidant activity against DPPH, crocin and beta-carotene were investigated. Results: All extracts were tested and a selection of known compounds significantly (p < 0.05) inhibited mouse ear edema. The results showed that CH2Cl2 extracts of roots and stems from P. gentianoides and ethyl acetate extracts of leaves from P. gentianoides and P. campanulatus, as well as luteolin, diosmetin, penstemide and verbascoside produced the most positive results. Of all substances tested, the CH2Cl2 extract of P. gentianoides roots was the most powerful inhibitor (ED50 = 0.07 mg/ear), with activity comparable to that of indomethacin. These extracts, compounds purified, as well as known compounds, inhibited oxidation of beta-carotene and crocin. Discussion and conclusion: These findings showed that the iridoid monoterpenes, flavonoids and phenylpropanoids present in these plants species may all contribute to the observed anti-inflammatory activity. Additionally, the observed antioxidant activity is correlated with the anti-inflammatory activity of these plants and the phytochemicals derived from them.