Leaf nutritional composition and calcium speciation of a karst-endemic wild vegetable used by the indigenous people of Hainan Island, China

<i>Primulina heterotricha</i>, a species endemic to Hainan Island, China, belongs to the Gesneriaceae family and is traditionally consumed as a wild vegetable by the Li ethnic group, the earliest inhabitants on the island. Despite its long history of use, systematic research on this species has been lacking. This study presents the first comprehensive analysis of the nutritional composition of <i>P. heterotricha</i>. The results reveal a high moisture content (95.4 g/100 g), and is rich in dietary fiber (2.95 g/100 g); it is characterized by low energy value (3.72 kcal/100 g) and low carbohydrate content (0.709 g/100 g). Notably, the species is characterized by exceptionally high calcium levels (289 mg/100 g), of which the predominant form is NaCl-Ca (133 mg/100 g), while other forms include H₂O-Ca (67.8 mg/100 g), AIC-Ca (55.9 mg/100 g), HCl-Ca (15.3 mg/100 g), Res-Ca (8.80 mg/100 g), and HAC-Ca (8.60 mg/100 g). These findings not only confirm the high nutritional value of <i>P. heterotricha</i> as a calcium-rich wild vegetable resource but also underscore its potential applications in functional foods, the development of local specialty ingredients, and the preservation of the traditional dietary culture of the Li ethnic group. Moreover, this work provides a solid foundation for further research on its food industry applications and highlights the importance of documenting and safeguarding ethnobotanical knowledge in minority-inhabited regions of Hainan Island.