Polymorphism in Calotropis procera: variation of metabolites in populations from different phytogeographical regions of Egypt

The present study aimed at investigating the phytochemical polymorphism among and within Calotropis procera populations collected from different phytogeographical regions in Egypt. A total of 128 individuals were collected from six different localities (New Valley, Aswan, Wadi Feran, Nuweibaa, Cairo-Suez Road and Al-Arish). There was a significant difference in primary (carbohydrates and proteins) and secondary (cardiac glycosides and flavonoides) metabolites among different populations. The maximum values of carbohydrates (163.0 mg g−1) and cardiac glycosides (15.2 mg g−1) were recorded in the population from Wadi Feran, while the minimum (90.2, 9.5 mg g−1) were recorded from Cairo-Suez road and New Valley, respectively. On the other hand, proteins had its highest concentration (263.8 mg g−1) in Aswan and the lowest (186.9 mg g−1) from Arish. Flavonoides attained their maximum (1.3 mg g−1) in Al-Arish and minimum (0.9 mg g−1) in Nuweibaa. Within population, the primary and secondary metabolites had significant variations where carbohydrates ranged between 106.9 and 162.6 mg g−1, proteins 217.2 and 273.4 mg g−1, cardiac glycosides 11.5 and 16.4 and flavonoides 0.9 and 1.3 mg g−1. Phytochemical characteristics classified C. procera populations into three clusters: (A) Aswan and Cairo-Suez road, (B) New Valley, Wadi Feran and Nuweibaa and (C) Al-Arish. Proteins had significant negative correlations with soil chlorides, calcium, magnesium and potassium, while flavonoides had significant positive correlation with chlorides, sodium and potassium. The study emphasizes the importance of population studies that may help in relating phytogeographical affinities with plant phytochemical characteristics and local ecological properties. It may also be useful in selecting populations with the maximum concentrations of metabolites for their economic use.