, changes occur rapidly. The biochemicals measured in ginkgo leaf extracts, in HDAC inhibitor the present study, are on the higher side as compared to the earlier reports from other countries.13 and 14 The 5 locations in the present study, falling between 1742 and 2260 m altitude representing temperate climatic conditions,

are likely to be associated with the higher contents of phytochemicals and antioxidants. Findings on production of polyphenols and antioxidants, in respect to environmental stress, have been linked to the defense mechanism.15 Total phenolic content in ginkgo leaf extracts varied significantly with respect to season and organic solvent, being maximum in autumn (Fig. 2A). Phenolic content was exceptionally higher in rainy and spring season in EA and n-B. Total flavonoid content

was higher in spring in 3 solvents, AW, WE and n-B, during rainy season in ME and during autumn in EA (Fig. 2A). FG-4592 Antioxidant activity performed by three assays showed significant variation with respect to the seasons, maximum being in ABTS and DPPH in autumn (Fig. 2B). In case of FRAP, higher activity was recorded during spring followed by autumn (Fig. 2B). Importance of seasonal variation in accumulation of total phenolic and flavonoid contents and antioxidants has been recognized. Although a clear and regular trend due to seasonal variation was not observed in the present study, the total phenolic content was relatively higher in autumn. Kobus et al13 reported higher level of polyphenols in October as compared to August. Besides, higher accumulation of phenolic and flavonoids during winter is likely to be attributed to the stress conditions such as temperature and plant growth stage. In general, the secondary metabolites remain at low level in ginkgo during spring and summer which are the initial stages for the growth of shoots and leaves. Afterward, towards autumn and winter, as the growth and metabolism become slower, the phytochemicals tend to accumulate in higher

amounts. The optimization experiments conducted for preference of solvent revealed that AW was the best solvent for extracting phenolic content in all the three seasons; followed by ME > WE > n-B > EA. Similarly, total PAK6 flavonoid content was recorded highest in AW during rainy and autumn followed by ME during spring (Fig. 3A). Different solvent systems also influenced the extraction of antioxidant activity in different seasons. Antioxidant activity measured by ABTS assay was highest in ME in rainy and autumn and in WE in spring. In DPPH assay, the activity was recorded highest in WE in all the seasons. Also, the reducing power assay showed higher antioxidant activity in AW during all the seasons (Fig. 3B). Factorial analysis exhibited that the solvents and seasons individually and their interaction significantly (p < 0.001) influenced the accumulation of phytochemicals and antioxidant activity ( Table 1).