It is believed that Chinese Broccoli is a descendant of cabbage.
The early Portuguese explorers first brought cabbage to Asia. Through years of breeding Chinese Broccoli have been developed from the cabbage the Portuguese had brought cabbage with them.
Unlike broccoli where you only eat the head are you also eating the stems and leaf on the Chinese Broccoli, the taste is close to broccoli but a bit sweeter.
I can not find much about the history of Chinese Broccoli. You will also find it under the name kai-lan/gai-lan which is the Cantonese name.
The nutrient fact, below, is based on 100 gram of fresh Chinese Broccoli.
Vitamin C, total ascorbic acid mg 29.6
Thiamin mg 0.1
Riboflavin mg 0.153
Niacin mg 0.459
Vitamin B-6 mg 0.074
Folate, DFE µg 104
Vitamin B-12 µg 0
Vitamin A, RAE µg 86
Vitamin A, IU IU 1720
Vitamin E (alpha-tocopherol) mg 0.5
Vitamin D (D2 + D3) µg 0
Vitamin D IU 0
Vitamin K (phylloquinone) µg 89.1
Fatty acids, total saturated g 0.116
Fatty acids, total monounsaturated g 0.053
Fatty acids, total polyunsaturated g 0.347
Cholesterol mg 0
Water g 92.55
Energy kcal 30
Protein g 1.2
Total lipid (fat) g 0.76
Carbohydrate, by difference g 4.67
Fiber, total dietary g 2.6
Sugars, total g 0.88
Calcium, Ca mg 105
Iron, Fe mg 0.59
Magnesium, Mg mg 19
Phosphorus, P mg 43
Potassium, K mg 274
Sodium, Na mg 7
Zinc, Zn mg 0.41