Evaluation of a chemotype of spearmint (Mentha spicata L.) grown in Siwa Oasis, Egypt

A distinguishable chemotype of spearmint (Mentha spicata) was found in Siwa Oasis, Egypt. The locals in very limited areas grow this type. Stolones of this type were transplanted to some other locations in Egypt namely; Owainate, Kharga, Samallot, and Arish. The oil content in the air-dried herb grown in Siwa reached 2.93 and 2.99% in the seasons of 2001 and 2002, respectively. The oil content of that type increased to 3.85 and 3.90%, in the two seasons when it was cultivated in Owainat territory, while it decreased to 1.59 and 1.61% when cultivated in Arish territory. These two geographical locations greatly differed in the average, maximum and minimum temperatures, relative humidity, sunshine duration, and solar radiation. Samples of spearmint distributed in the local market and cultivated around Cairo contained only 1.28% oil. In oils of Siwa mint cultivated in the different locations, carvone was the main constituent; its content ranged between 42.23 and 57.61%, while limonene came in the second rank ranging between 26.15 and 34.83%. In contrast, oil of spearmint collected from the local market (grown in Cairo) was characterized by higher carvone (73.18%) and lower limonene (5.00%) contents. Siwa mint is a distinguishable type of spearmint regarding its oil content and composition.