## 1 Introduction  
In recent years, there has been a great interest in incorporating edible flowers into human food [1]. Flowers have played an important role in food preparation, being frequently used as a fresh garnish in various dishes, or as a key ingredient in jams, cakes, yogurts, desserts, and ice creams, and even consumed directly as vegetables [2]. In these situations, the of using flowers is to improve the appearance, color, taste, and nutritional value of foods [3]. Throughout history, the use of flowers has been documented, mainly in food processing, in Roman, Chinese, Indian and Middle Eastern cultures [3]. The recent interest in including edible flowers in the human diet is mainly due to their nutritional contribution and the possible beneficial effects for health, as well as the likelihood of preventing some diseases associated with oxidative stress [4, 5]. These benefits have been associated with the intake of different bioactive compounds such as flavonoids, anthocyanins, carotenes, terpen, alkaloids, vitamins, minerals, peptides, and essential oils [6, 7]. Moreover, flowers have been shown to possess diverse biological properties, including antioxidant, antibacterial, antiproliferative, anti-obesity, hypoglycemic, neuroprotective, hepatoprotective, and anti-inflammatory activities [6, 8].  
Cactaceae are native plants of North America, with flowers which are also used in food. Cactaceae comprise about 1500 species, of which there are approximately 700 species in Mexico, grouped into 68 genera. They are considered an important part of the vegetation of arid and semiarid regions, playing an important role in culture and human populations; indigenous peoples use more than 150 species of Cactaceae, of which 50 are the most commonly cultivated for various purposes [9]. Among them, flowers for human consumption such as agave, garambullo and aloe flowers [10] are grown; these have high contents of bioactive compounds such as phenolic compounds, ascorbic acid, and carotenoids, to which good antioxidant capacities are attributed. In Mexico, in the state of Hidalgo, there is an arid surface area of 39% [11], where Cactaceae such as Cardon (CA) (_Cylindropuntia rosea_), Xoconostle Ulapa (XU) (_Opuntia oligacantha_), Xoconostle Cuaresmeno rosado (XC) (_Opuntia matudae_), and Pitaya (PI) (_Echinocreus cinarcascens_) are very common. These Cactaceae are commercially important mainly for their fruits, although the flowers are also used as food mainly in rural communities in different types of traditional dishes, and are also consumed by animals as fodder [12]. However, in their contribution to the diet and as a health benefit to those who consume them, their nutraceuticalal properties are unknown. Similarly, the use of these flowers is limited by the difficulty of their application as a possible food ingredient, and the lack of knowledge about their nutritional and functional potentials. There are also no data on the identification of toxic compounds or allergenic and antinutritional factors that could compromise consumer health, or guarantee the quantities that are safe for consumption. In order to begin to obtain knowledge about the flowers of Cardon, Xoconostle and Pitaya as a possible source of bioactive compounds for use in the food industry, the objective of this work was the evaluation of their functional, nutritional composition, and the identification of their main metabolites by HPLC/ESI/MS.