Differential concentrations of NaCl and K2Cr2O7 stress 1 conditions: Biophoton characteristics and quality prediction 2 feasibility analysis of fresh Nepeta cataria L. leaves

Ruyu Wang¹Jiahui Luan²ZhiYing Wang¹Baorui Cao²Yiwei Chen¹Xue Li¹Tingting Deng³Jinxin Du¹Jinxiang Han^1*Meina Yang^1*

• ¹Shandong First Medical University, Jinan, China
• ²Shandong University of Traditional Chinese Medicine, Jinan, China
• ³Shandong Women's University, Jinan, China

Introduction: Nepeta cataria L. (NcL), a perennial medicinal plant, is used to 14 dispel wind-heat, remove blood stasis, and reduce swelling. However, soil salinization 15 and heavy metal pollution have severely impacted its growth and quality. Current 16 quality assessments, based solely on pulegone (PG) content in the final product, 17 neglect cultivation process controls. 18 Methods: We applied biophoton detection to differentiate stress types in fresh NcL 19 leaves and explored the correlation between biophoton emission and plant quality. 20 Spontaneous photon emission (SPE) and delayed luminescence (DL) were measured 21 under NaCl and K2Cr2O7 stress. Key parameters, including counts per second (CPS) 22 and initial intensity (I0), were analyzed. PG content was determined via ultra-high 23 performance liquid chromatography, alongside physiological and oxidative stress 24 indexes. 25 Results: Stress conditions significantly inhibited NcL growth and quality, leading to 26 marked differences in biophoton emission, physiological and biochemical indicators, 27 oxidative stress indexes and PG content between stress and control groups. For 28 instance, in the 120 mmol/L NaCl group, the CPS decreased by 54.27%, while I0 29 dropped by 54.12%. PG content in high-salinity groups was 1.22 mg/g, 40.19% lower 30 than controls (2.04 mg/g). CPS and I0 strongly correlated with PG content (r = 0.89 31 and r = 0.85, respectively), as well as with physiological and oxidative indicators. 32 These relationships were clearly visualized. 33 Discussions: Our study demonstrates the potential of biophoton detection for 34 quality evaluation during NcL cultivation. We identified specific biophoton 35 parameters that reflect plant quality, offering a new approach for process-based 36 quality control.