Identification of bioactive phenolics from Porana sinensis Hemsl. stem by UPLC-QTOF-MS/MS and the confirmation of anti-inflammatory indicators using LPS-induced RAW264.7 cells

To characterise bioactive phenolics and confirm anti-inflammatory indicators in Porana sinensis stem, 23 phenolics were identified by UPLC-QTOF-MS/MS from crude extract (CE) prepared optimally with 80% methanol. Further fractionalisation using D101 macroporous resin resulted in predominant enrichment of total phenols and flavonoids into Fr.II. Correspondingly, the bioactive components-enriched Fr.II exhibited the lowest IC₅₀ for scavenging DPPH and ABTS and the highest oxygen radical absorbance capacity or ORAC followed by Fractions Fr.I + Fr.II, CE and Fr.I, implying that certain phenolics possessing lower antioxidant activity completely remained in CE. Anti-inflammatory tests with LPS-stimulated RAW264.7 cells showed that CE possessed the highest inhibition of NO-production followed by Fr.II and Fr.I, meaning that CE might contain compounds that expressed higher anti-inflammatory but lower antioxidant activities or possessed synergistic interactions but were not fractionated together. Quantitative determination of nine major phenolics revealed that caffeic acid and 3-, 4- and 5-caffeoylquinic acids were concentrated into Fr.I, whereas scopolin, scopoletin and 3,5-, 3,4- and 4,5-dicaffeoylquinic acids were enriched into Fr.II. Further experiments with three selected major phenolics reduced the proposed synergistic interactions. Anti-inflammatory tests of the nine major phenolics evidenced that caffeic acid and the six caffeoylquinic acids produced higher, and the three dicaffeoylquinic acids at 140 μΜ showed even more significant activities in suppressing NO-production and mRNA expression of iNOS, TNF-α, COX-2, and IL-6, suggesting that these three dicaffeoylquinic acids could be indicators of the anti-inflammatory potential of P. sinensis stem. These findings provided novel insights for potential use of P. sinensis or liana, as an important source of natural antioxidants, against inflammation.