Diversity in photosynthetic pigments and phytochemical compounds among Iranian populations of Inula helenium L.

Elecampane (Inula helenium L.) is a valuable medicinal plant that has anticancer, cardioprotective, antibacterial and anti-inflammatory properties.. This study was conducted with the aim of evaluating 15 different populations of Iranian elecampane collected from their natural habitats in terms of content of proline, photosynthetic pigments, total phenol (TPC) and total flavonoid (TFC), as well as essential oil (EO) profile. The content of total phenol, total flavonoid and proline was different among the populations, and TPC showed a positive and significant correlation with the content of Chl, carotenoid and proline. Also, the TFC was significantly positively correlated with total chlorophyll and negatively correlated with proline. The amount of essential oil was significantly negatively correlated with total chlorophyll, carotenoid and TPC. The essential oil (EO) content of the populations varied from 0.13% to 0.26%, and their analysis by GC/MS revealed 33 compounds comprising over 96% of the EO content. The main compounds in the EO profiles included β-elemene, tricyclene, α-pinene, isoalantolactone, and santolina triene. Principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) revealed three classes based on the main EO compositions. The populations in habitats with altitudes of 2000–2400 m, pH levels of 6.5–7, and soils with silt/silt loam texture had higher TPC and EO content. Importantly, different populations exhibited essential oils with highly diverse compositions, with some populations containing compounds absent in others. Except for β-elemene, which was present in all populations, other compounds varied in presence and quantity across different populations. This suggests the potential for obtaining diverse and desired chemotypes of Inula helenium through further research.