Extraction optimization and constituent analysis of total flavonoid from Hosta plantaginea (Lam.) Aschers flowers and its ameliorative effect on chronic prostatitis via inhibition of multiple inflammatory pathways in rats

Abstract

Ethnopharmacological relevance: Hosta plantaginea (Lam.) Aschers flowers (HPF) are well-known for their high flavonoid content, which contribute to their widely as traditional Chinese medicine for alleviating inflammation. Despite their recognized potential, information regarding the total flavonoid (TF) of HPF and its therapeutic application in treating chronic prostatitis (CP) remains unknown.

Aim of the study: We aimed to investigate the extraction optimization, constituent analysis, and alleviating effect of TF on CP as well as its potential mechanism.

Materials and methods: The optimized extraction of TF from HPF was explored using response surface methodology with a Box-Behnken design model. The major flavonoids in TF were identified based on UHPLC-MS approach. Efficacy of TF (25 and 100 mg/kg, p.o.) on CP was evaluated in prostate antigen emulsion-induced autoimmune CP rat model by measuring prostatic index, the levels of leukocytes and lecithin bodies, as well as histopathological examination. The protein expression contents were detected by western blotting. Additionally, the antioxidant (DPPH and ABTS) and anti-inflammatory (cyclooxygenase 2, COX-2 inhibitory) effects of TF were also evaluated in vitro.

Results: The optimized conditions for TF extraction were determined as 60% ethanol concentration, 30 mL/g liquid-to-solid ratio, 30 min extraction time, and 90 °C extraction temperature, and the extraction ratio is 65.98 ± 2.14%. A total of 15 major flavonoids in TF were characterized by comparison with reference standards. TF ameliorated the efficacy of CP in rats in a dose-independent manner, including reduced prostatic index and leukocytes levels, elevated lecithin body levels, ameliorated histopathological damage to prostate, and suppressed phosphorylated protein expressions of nuclear factor kappa-B (NF-κB) p65, inhibitor of NF-κB alpha (IκBα), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (Erk), just another kinase 1 (JAK1), signal transducer and activator of transcription 3 (STAT3), phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt). Simultaneously, the IC₅₀ of TF to DPPH, ABTS radicals, and COX-2 were 2.02, 1.79, and 0.0838 mg/mL, respectively.

Conclusions: We first demonstrated that TF from HPF represents a promising candidate to alleviate CP through suppression of NF-κB, MAPKs, JAK-STAT, and PI3K-Akt signaling pathways.

Keywords: Chronic prostatitis; Constituent analysis; Extraction optimization; Hosta plantaginea flowers; NF-κB/MAPKs/JAK-STAT/PI3K-Akt pathways; Total flavonoid.