Iridoid Glycosides and Phenolic Compounds from the Flowers of Vitex agnus-castus

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A new and rare type of iridoid glycoside, agnusoside (1), a new caffeoylquinic acid derivative, castusic acid (2), and a new sugar ester, 1,2‐di‐(4‐hydroxybenzoyl)‐β‐glucopyranose (3), along with ten known compounds belonging to iridoid glycosides (agnuside, trans‐eurostoside), caffeoylquinic acid derivatives (chlorogenic acid and isochlorogenic acid A), flavonoids (isoorientin, isovitexin, kaempferol 3‐O‐sophoroside, luteolin 6‐C‐(2′′‐O‐trans‐caffeoyl)glucopyranoside, and simple phenolic acids (4‐hydroxybenzoic acid, 3,4‐dihydroxybenzoic acid), chemical classes were isolated from the flowers of Vitex agnus‐castus. The structures of the isolates were established by extensive 1D‐ and 2D‐NMR spectroscopic analysis as well as HR‐ESI‐MS. Agnusoside (1) represents an unusual type of iridoid glycoside with its 6‐keto C(4) nonsubstituted aglycone.