This research studied the influence of phytochemical compounds on the germination time of pigeon pea (Cajanus cajan (L.) Huth). Over the 72 hours germination period, the contents of total and most individual free amino acids, particularly histidine, showed substantial increases. The content of γ-aminobutyric acid (GABA) was also greatly increased, from 0.24 µg/g to 2.7 µg/g, representing a nearly ninefold increase. The total phenolic content (TPC) and total flavonoid content (TFC) were positively related with germination time, with TPC highest at 62.49 mg GAE/100 g DW at 72 h, and TFC increased from 18.87 mg RE/100 g DW to 30.05 mg RE/100g.DW at 72 hours. The contents of individual phenolic acids and flavonoids, such as, protocatechuic acid, p-coumaric acid, ferulic acid and rutin, experienced noticeable increases. However, vanillic and catechin were only detectable at 72 hours, respectively. Antioxidant capacity measured by DPPH and FRAP assays increased from 102.30 to 128.95 mgTE/100g DW and 694.13 to 836.93 mg FeSO₄/100g DW mmol/g, respectively, and therefore highlighting the enhanced antioxidant potential of germinated pigeon pea. The results from Fourier-transform infrared spectroscopy (FTIR) supported these findings. The study emphasizes the potential of germination to enhance the phytochemical compounds of pigeon pea seeds.

Cajanus cajan (L.) Huth (Fabaceae) is a food legume of considerable nutritional and functional significance. This study examined the comparative effects of salt stress on seed germination, hydroponic growth, and phytochemical accumulation across two developmental stages: 10-day-old germinated seeds and 45-day-old hydroponically grown plants, using NaCl solutions at concentrations of 0, 25, 50, 75, 100, and 150 mM. Both germination rate and growth were greatest at 0–25 mM NaCl, with performance declining at higher concentrations. LC–MS/MS analysis of free amino acids in 10-day-germinated seeds revealed a salt-induced metabolic shift. Proline, leucine, and phenylalanine were the dominant free amino acids and increased progressively with rising NaCl concentrations. Phytochemical profiling by HPLC identified gallic acid, catechin, and genistin as the major compounds, with increased levels under salinity stress. Germinated seeds at 150 mM NaCl, germinated seeds exhibited the highest phytochemical accumulation, with total phenolic content (TPC), total flavonoid content (TFC), and DPPH activity reaching 18.192 ± 0.020 mg GAE/g extract, 8.519 ± 0.026 mg QE/g extract, and 11.623 ± 0.284 mg AAE/g extract, respectively. Phytochemical responses in 45-day hydroponic plants varied by tissue type. Leaves exhibited declining TPC and TFC with increasing NaCl (from 29 to 16 mg GAE/g and 41 mg QE/g extract), while stems showed the opposite trend, reaching 18 mg GAE/g and 21 mg QE/g extract at 50 mM. Root tissues maintained comparatively low phytochemical levels throughout. Notably, DPPH scavenging capacity increased across all tissues under salt stress, with peak values of 12–13 µg AAE/g extract recorded at 50 mM NaCl. These results indicate that salt stress exerts stage- and organ-dependent effects on phytochemical accumulation in C. cajan. High salinity during germination stimulates bioactive compound production, whereas moderate salinity appears to be the threshold at which antioxidant capacity is maximized in hydroponic systems. These observations point to the practical utility of controlled salt elicitation as a strategy for enriching pigeon pea with health-promoting phytochemicals, reinforcing its potential as a functional food crop.