Development of an at-line coupling of LC-QTOF-ESI-MS/MS to steroid 5-alpha reductase inhibition assay, a fast bioactive targeting and guided purification of natural complex sample, Impatiens balsamina Linn

[Display omitted] •Rapid screen by at-line LC-ESI-QTOF-MS/MS coupled to S5αR inhibitory assay.•2-Methoxy-1,4-naphthoquinone (2MN) from I. balsamina identified as S5αR inhibitor.•2MN with 8-fold and 72-fold greater potency than finateride and curcumin.•Isolated 2MN and impatienol, exhibited a therapeutic index exceeding 100. This study provides a rapid and accurate method for screening steroid 5-alpha reductase (S5αR) inhibitors in Impatiens balsamina Linn (IB). using at-line LC-QTOF-ESI-MS/MS coupling S5αR inhibitory assay. IB (Balsaminaceae) is an annual herbaceous plant cultivated in tropical and subtropical regions. It has been used in traditional Chinese and Thai medicine for treatment of hair loss and various skin conditions, potentially through anti-androgenic mechanisms. A combined approach of S5αR inhibitory assay and LC-QTOF-ESI-MS/MS was developed to rapidly screen for target biomarkers and guide their isolation using preparative HPLC. The toxicity of both the extract and isolated biomarkers was evaluated on skin cells, keratinocytes, and fibroblasts. Eight bioactive compounds were identified as two naphthoquinone, two fatty acid derivatives, three nitrogenous compounds and one aromatic derivative. The most potent bioactive markers, identified as 2-methoxy-1,4-naphthoquinone (2MN) and impateinol, were targeted and isolated using preparative HPLC, yielding 5.0 % and 3.5 %, respectively. These compounds exhibited S5αR inhibitory activity higher than that of finasteride drug by 10 and 2 times, respectively. Both the isolated biomarkers and the extract demonstrated a broad therapeutic index. The developed method in this study proved to be both rapid and accurate, making it suitable for screening and targeting S5αR inhibitors in herbal plants or complex matrix samples. It facilitated the fast-guided isolation of bioactive compounds, highlighting its potential for future applications in drug discovery research.