Evaluation of Phytochemistry, Toxicity and Radical-Scavenging Capacity of Two Erigeron Species (E. annuus (L.) Pers. and E. strigosus Muhl. ex Willd.) Extracts.

Erigeron sp. has been employed for medicinal purposes in the ethnopharmacology of numerous countries worldwide, as well as in modern-day herbal applications. Their healing capacity is determined by their bioactive compound content, with polyphenols playing a predominant role. Phytochemistry of two alien species in Lithuania, E. annuus (L.) Pers. and E. strigosus Muhl. ex Willd. was investigated. The phytochemicals in the extracts of flowers, leaves and roots were identified by the HPLC/DAD/TOF technique. Some acids, such as fumaric, succinic, quinic, malic, protocatechuic, p-coumaric, gelseminic and (iso-, neo-) chlorogenic, were found in the extracts of both investigated Erigeron species. Additionally, flavonoids and other constituents were tentatively identified in the plant extracts. Umbelliferone, loliolide, kaempferol/luteolin, erigeside I, baicalin, quercetin and its glucoside, apigenin and its glucuronide, apigenin-7-O-glucuronide-6'-ethyl ester, astragalin/quercitrin, scutellarin, caffeoylshikimic acid glucoside, sesquiterpene hydrocarbon(s) and rutin were found to be common compounds in all extracts. A toxicity test using brine shrimp Artemia sp. larvae revealed that the activity order between both fleabane organs was as follows: leaves > flowers > roots. E. strigosus extracts exhibited slightly stronger toxic effects than E. annuus. Total phenolic content (TPC) varied from 11.88 ± 1.27 to 304.94 ± 3.81 (mg/L, expressed in gallic acid equivalent (GAE)) in aqueous E. annuus root and methanolic E. strigosus leaf extracts, respectively. TPC and antioxidant ability differed significantly between the plant organs of both fleabanes. ABTS●+ and DPPH● scavenging capacity was detected for aqueous extracts of both Erigeron species, ranging from 0.16 ± 0.02 (ABTS●+) to 17.55 ± 0.07 (DPPH●) (mmol/L, TROLOX equivalent) for E. strigosus roots and E. annuus leaves, respectively. A strong positive correlation between TPC and ABTS●+ scavenging capacity was determined (p = 0.01996 and p = 0.01171 for E. annus and E. strigosus extracts, respectively), while the correlation between TPC and DPPH● assay values was also positive, but did not reach statistical significance (p > 0.05). For the first time, the data concerning the phytochemistry, toxicity and radical-scavenging capacity of E. strigosus have been documented. The present study makes a substantial contribution to studies already existing on bioactive phytochemicals of E. annuus, with a particular focus on E. strigosus plants.