Free Proline Distribution in Solanum surattense from Rajasthan
Abstract
Solanum surattense Burm.f. (Solanaceae) is a medicinally important herb widely distributed in the tropical and subtropical regions of India, including the arid and semi-arid areas of Rajasthan. The species is valued for its diverse ethnomedicinal and pharmacological properties and has been extensively studied for its phytochemical constituents. However, limited information is available regarding its biochemical adaptations to environmental stress, particularly proline metabolism. Proline is a key osmoprotectant that accumulates in plants under adverse conditions and plays a significant role in osmotic adjustment, membrane stabilization, redox regulation, and stress tolerance. The present study aimed to evaluate the organ-specific distribution of free proline in S. surattense collected from the Atoon region of Bhilwara District, Rajasthan. Free proline content was estimated in root, stem, leaf, fruit, and seed samples using the acid-ninhydrin colorimetric method of Bates et al. (1973), and absorbance was measured at 540 nm. The results revealed marked variation in proline accumulation among different plant organs. The highest proline content was recorded in the stem (0.4660 mg/gdw), followed by fruit (0.3731 mg/gdw), seed (0.2840 mg/gdw), leaf (0.1811 mg/gdw), and root (0.1462 mg/gdw). The stem exhibited nearly threefold higher proline concentration than the root, suggesting its important role in osmotic regulation, metabolite transport, and physiological adaptation under water-limited conditions. Moderate accumulation in fruits and seeds may be associated with reproductive development and storage functions. The observed pattern highlights the differential allocation of proline within plant organs and reflects the adaptive strategies of S. surattense in semi-arid environments. These findings provide baseline biochemical information and contribute to understanding the stress physiology and ecological resilience of this medicinally important species.
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Introduction
The genus Solanum surattense Burm.f. (Family: Solanaceae) is found in all districts of Tamil Nadu as well as tropical and subtropical regions of Australia, Malaysia, South East Asia, and India (Mathew, 1983). There is discussion of S. surattense's various therapeutic qualities (Chopra et al., 1956; Kirtikar & Basu, 1935; Anonymous, 1986; Mudhaliar, 1988).
In arid and semi-arid regions with limited access to water, aridity is a significant abiotic factor affecting plant growth, productivity, and ecosystem functioning. Climate change-related increases in aridity put plants under physiological stress, which triggers a variety of adaptation processes. One of the most crucial biochemical strategies for preserving cellular homeostasis, osmotic balance, and stress tolerance under water-deficit conditions is the accumulation of compatible osmolytes like proline (Handa et al., 1986; Ashraf & Foolad, 2007; Verbruggen & Hermans, 2008; Szabados & Savouré, 2010).
The most significant environmental limitation that affects ecosystem structure and functioning is aridity, which restricts water availability and puts plants under physiological stress (Harpole & Suding, 2011). Plants frequently display adaptive biochemical responses to rising aridity brought on by climate change, such as the buildup of osmoprotectants like proline, to preserve cellular homeostasis and improve stress tolerance (Trenberth et al., 2014). Flavonoids, alkaloids, phenolic compounds, steroids, and glycosides are among the many bioactive components of the medicinally significant species Solanum surattense Burm.f. that contribute to pharmacological actions, including its many anti-inflammatory, hepatoprotective, antiasthmatic, and antioxidant qualities (Tekuri et al., 2019). Traditional medicine promotes significant use of Solanum surattense, a plant rich in bioactive phytochemicals (Boomiga et al., 2021).
Its physiological response to environmental stress, especially proline buildup, is still not sufficiently understood. The environmentally adapted medicinal plant Solanum surattense Burm.f. is recognized for its extensive range of pharmacological actions and rich phytochemical composition (Hasan et al., 2024). Recent investigation on ecophysiological studies have revealed that populations of Solanum surattense Burm.f. living in hyper-arid conditions accumulate far more free proline than populations from somewhat less stressed situations. The significance of proline metabolism in this medicinal species' adaptive strategy was highlighted by the positive correlations found between elevated proline concentration and improved osmotic adjustment, maintenance of cellular hydration, protection of photosynthetic machinery, and increased tolerance to drought-induced oxidative stress (Rafiq et al., 2025).
Conclusion
Using the acid-ninhydrin colorimetric method, the current study successfully measured and compared the total free proline content of five distinct organs of Solanum surattense Burm.f. that were taken from the Atoon region of Bhilwara, Rajasthan: root, stem, leaf, fruit, and seed. In comparison to primarily absorptive and photosynthetic organs, structural, reproductive, and storage-associated organs accumulate significantly higher levels of this osmoprotectant, according to the results, which showed a clear organ-specific pattern of proline accumulation in the order stem > fruit > seed > leaf > root.
These findings show that proline has a specific and organ-specific function in Solanum surattense's physical adaptation, possibly supporting osmotic control, structural stability, and reproductive defense in the semi-arid climate of the Aravalli region. The nearly threefold higher proline concentration in the stem compared to the root underscores the importance of this organ in osmotic regulation and stress adaptation.
Since S. surattense is a well-known medicinal species, the current biochemical data not only improves our knowledge of its stress physiology but also establishes a basis for future studies that relate osmolyte accumulation to its pharmaceutical importance and ecological resilience. The organ-specific distribution of proline may influence the production and accumulation of bioactive compounds, which are responsible for the species' medicinal properties.
References
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