Secondary Metabolites and Their Biological Evaluation from the Aerial Parts of Sibth. & Sm. (Asteraceae).

Phytochemical investigation of Sibth. & Sm. resulted in the isolation of twenty-two natural products: eleven sesquiterpene lactones, artemorin (), tamirin (), tanachin (), reynosin (), baynol C (), desacetyl-β-cyclopyrethrosin (), 1β-hydroxy-4α-methoxy-5α,7α,6β-eudesm-11(13)-en-6,12-olide (), 1β,4α,6α-trihydroxyeudesm-11-en-8α,12-olide (), 1β-hydroxy-arbusculin A (), methyl-1β,4α,6α-trihydroxy-5α,7αH-eudesm-11(13)-en-12-oate () and methyl-1β,6α,8α-trihydroxy-5α,7αH-eudesma-4(15),11(13)-dien-12-oate (); one lignan, pinoresinol (); one norisoprenoid, loliolide (); six flavonoids (four genins and two glycosides), hispidulin (), nepetin (), jaceosidin (), eriodictyol (), eriodictyol-3'-O-β-D-glucoside () and eriodictyol-7-O-β-D-glucuronide (); and three phenolic derivatives (one phenolic acid and two phenolic glucosides), protocatechuic acid (), arbutin () and nebrodenside A (). From the isolated compounds, only nepetin () has been reported previously from the genus and, to the best of our knowledge, it is the first time that compound () has been identified in Asteraceae. A number of these substances were tested for (a) inhibition of lipoxygenase and acetylocholinesterase, (b) their antioxidant activity using the DPPH (1,1-Diphenyl-2-picrylhydrazyl) method or/and (c) inhibition of lipid peroxidation. The tested components exhibited low antioxidant activity with the exception of and , while the effectiveness of these compounds in the inhibition of acetylocholinesterase is limited. Furthermore, Molinspiration, an online computer tool, was used to determine the bioactivity ratings of the isolated secondary metabolites. The compounds' bioactivity ratings for potential therapeutic targets were very promising.