Uhplc‐esi‐qtof‐ms/ms‐based molecular networking guided isolation and dereplication of antibacterial and antifungal constituents of ventilago denticulata

Abstract

Ventilago denticulata is an herbal medicine for the treatment of wound infection; therefore this plant may rich in antibacterial agents. UHPLC‐ESI‐QTOF‐MS/MS‐Based molecular networking guided isolation and dereplication led to the identification of antibacterial and antifungal agents in V. denticulata. Nine antimicrobial agents in V. denticulata were isolated and characterized; they are divided into four groups including (I) flavonoid glycosides, rhamnazin 3‐rhamninoside (7), catharticin or rhamnocitrin 3‐rhamninoside (8), xanthorhamnin B or rhamnetin 3‐rhamninoside (9), kaempferol 3‐rhamninoside (10) and flavovilloside or quercetin 3‐rhamninoside (11), (II) benzisochromanquinone, ventilatones B (12) and A (15), (III) a naphthopyrone ventilatone C (16) and (IV) a triterpene lupeol (13). Among the isolated compounds, ventilatone C (16) was a new compound. Moreover, kaempferol, chrysoeriol, isopimpinellin, rhamnetin, luteolin, emodin, rhamnocitrin, ventilagodenin A, rhamnazin and mukurozidiol, were tentatively identified as antimicrobial compounds in extracts of V. denticulata by a dereplication method. MS fragmentation of rhamnose‐containing compounds gave an oxonium ion, C6H9O3+ at m/z 129, while that of galactose‐containing glycosides provided the fragment ion at m/z 163 of C6H11O5+. These fragment ions may be used to confirm the presence of rhamnose or galactose in mass spectrometry‐based analysis of natural glycosides or oligosaccharide attached to biomolecules, that is, glycoproteins.