Influence of Seasonal Variation on Phytochemical Composition and Biological Activities of Medicinal Plant Extracts

Abstract

Season is here as a major driver of how medicinal plants build chemicals. Over the year, changes in weather and growth timing shift-based aspects the number of secondary compounds made and kept in plant tissues in this way. Temperature, day length, rain, as well as humidity all matter. The plant phase also matters. These shifts-based structure can change the quality of plant-based medicines as also how dependable they are. This review in this nature to pulls together results from peer reviewed studies on how phytochemicals as well asbioactivity vary with seasons. It focuses on structure in here to be medicinal species tied to Himalayan & in this way North East Indian traditions. The species here by to maintain include herein Ocimum sanctum, Curcuma longa, Withania somnifera, Centella asiatica, Zanthoxylum armatum, as well as Acorus calamus, which has been studied for therefore in Pithoragarh in Uttarakhand. Other species covered are mostly observed here with Rosmarinus officinalis, Tinospora cordifolia, as well as Camellia sinensis, studied in Mokokchung in Nagaland in here. Across these species, seasonal patterns show up in this nature several measures. These include essential oil makeup, curcuminoid levels, withanolide levels, triterpene amounts, as well as biomarker glycoside concentrations, & in this nature total phenolic content. The antioxidant and antimicrobial strength also change with this particular season. In multiple cases, the best & most natured worst harvest times differ by about two to eleven-fold. One study here in lasting 24 months, dated 2025, looked at Tinospora cordifolia & backed the classic Ayurvedic monsoon collection guidance. It used here on with modern UHPLC quantification to do that. Another work used an 8-date harvest trial in turmeric. It found in this way to understand curcumin rose by around 65% from the earliest harvest-based nature to the latest harvest. Three patterns show up in the data. First, plants that here are hold fragrant oils in their tissues are more often gathered near late summer or late autumn based structure. Second, when the useful parts sit in roots or rhizomes, the active natured here with level tends to climb as the plant matures, rising in a steady way until in this way around January and February. Third, species that are known for stem traits or glycoside markers can easily shift the other way and may peak in the monsoon period like these. Taken together, these results here by line up with the older Ayurvedic idea about picking at the right time in this way, what is called in here ritu-anusara sangrahana. We also say here that the harvest season should be handled as a fixed factor in pharmacognostic work as well as in industrial sourcing. More studies are still hereby needed across more than one season, especially for plant based natured types that matter in Assam and the wider North East of India.