Elongation efficacy of radicles was effective in first three days11, similarly to results of this study, contrary to 3 to 4-day-germination in work of Zhou and Zhang12. Legumes are famous for total phenolic compounds rather than rice, corn, millet and wheat. Major classes of phenolic contents in beans and lentils have been gaining popularity due to antioxidant activity. The levels of natural endogenous antioxidants (e.g., phenolics, tocopherols; vitamin C) vary during seed germination of legumes. Federica et al.6 analysed 14 polyphenolic compounds ranging from 3 mg kg−1 for dehulled red lentils to 1630.5 mg kg−1 for ruviotto beans.
Legume fractions and germination time were affected on TPC. The total phenolic contents were increased after the germination. Similarly, the TPC contents were significantly (p < 0.05) increased with the germination time in seed hulls, radicles, cotyledons of legume13 and lentil seeds. Contrary results were shown by lentils and beans of Aguilera et al.14 and Duenas et al.15. No change in TPCs was shown by kidney beans, but the values were highly decreased in lentils16. Our results regarding TPCs were significantly higher than common bean seed coats (0.69-3.32 mg GAE/g) reported by Chávez-Mendoza et al.13.
The high amount of polyphenols were also found in black, brown, red beans17, adzuki bean18, and faba bean (40.7 to 66.1 mg g−1)19 extract, whereas low in pea20, broad beans21, lupins22, white beans23 and grass pea24. The dried beans of our black (1.70 mg GAE/g) and white chickpeas (1.83 mg GAE/g) possessed the lowest value of TPCs compared to Fenugreek (5.79 mg gallic acid/g), (56.14 mg gallic acid/g) and chickpea seeds (5.68 mg gallic acid/g), (57.94 mg gallic acid/g)25.
The TPCs of Lens culinaris (1.49 mg GAE/g) were lower amongst the remaining samples of this study (Table 1), similarly in lentils of Salem et al.26 (60.39 mg GAE/g), Nair et al.27 (1191 mg.kg−1) and Awada et al.28 (4730 mg. kg−1), whereas Amarowicz et al.7 and Zhao et al.29 demonstrated the highest phenolic content (47.6 mgg−1) in lentils than beans. Contrarily, maximum values were reported in red and green lentils7,30.
There are two schools of thought behind low level of TPCs during germination: 1) sprouting causes the reduction in flavan-3-ols and anthocyanin15; 2) reactive oxygen species (ROS) released from metabolically active cells of seed, which influenced the biological process of seed germination. ROS as a messenger transmits environmental signals during seed germination and responsible for lowering the antioxidant activity of bean and lentils after germination31. TPCs were decreased in peanuts, soybeans and lentils after germination32 contrary to this study (Table 1), while Khang et al.33 values were significantly increased during germination in all legumes. Zhaohui et al.34 investigated TPCs and antioxidant activity of germinated Mung beans, soybeans and black beans sprouts were highest initially (44.87–90.31%) then decreased.
In white lentils of this work, the TPCs were comparable to faba beans (7.11 mg gallic acid/g)35 and lupine seeds (8.56 mg gallic acid/g)36. Emily et al.37 worked on 14 Canadian pulses included beans, peas, lentils and analyzed antioxidant activity (1.16 to 7.45 mg GAE/g DW) and revealed that samples with dark testa (black lentils and diavoli beans) possessed higher antioxidant activity than pale testa.
Antioxidant capacity (AC) of legumes is due to active micro and macro elements (polysaccharides, vitamins, amino acids proteins)38. In this study, germinated lentils (Masoor) contained maximum ACs than dried lentils (Masoor) similarly the work of Dalaram et al.39 but contrary to lentils of Gubanenko et al.40 and Zhao et al.29. Researchers supported that AOA (Antioxidant activity) increased as the germination time increased25, e.g., in mung beans, soybeans, black beans33, lentil seeds41, kidney beans14,16, chickpea seeds, fenugreek seeds, lentil seeds26 and lupine seeds36. Though, black beans did not change AOA during the germination process42.
Gubanenko et al.40 revealed that seedlings of lentils show a slightly higher antioxidant activity than chickpea sprouts, whereas seeds of green pea, chickpea43 and faba beans39 dramatically contained maximum TAC. The seed coat of common bean exhibited greater antioxidant capacity (23.86–84.10%) than the cotyledon (0.66–29.77%) of all bean varieties13.
The most famous legumes with maximum antioxidant compounds in dietary fibres were found in chickpeas (Cicer arietinum), pulses44, white and red beans (Phaseolus vulgaris), which promote the health and prevent chronic diseases45. The result of this study regarding scavenging activity was similar to Saleh et al.25. They explained common beans (84.52%) contained highest radical scavenging activity than lupine seeds (78.29%). The values of lentils scavenging capacity of this study were significantly higher than 38.5%29.
The antioxidant activity of beans increased after germination and decreased in lentils depends upon type and conditions of germination46, similarly to this study, where free radical scavenging activity increased in germinated seeds depend on the time taken for germination. Wang et al.47 worked on Chinese beans, spring bay beans, black beans, pearl beans and determined the strong positive relationship between total phenolic contents and antioxidant activities. Black, red, green beans, red kidney beans and soybeans possessed higher total phenolic contents and antioxidant capacity, whereas red and yellow lentils (dhal) and chickpea possessed lower capacity48.