The Chinese market has multiple varieties of green vegetables beyond spinach and broccoli.
The greens provide lutein a fat-soluble phytonutrient that is concentrated in the eye where it helps to prevent age-related macular degeneration, the commonest cause of blindness in people over 65 years of age. Lutein concentrates in part of the eye called the macula which is actually nerve tissue linking to the brain. Lutein is concentrated in the brain about two fold over what is found in the blood. Ongoing research is linking lutein as an important phytonutrient for the brain.
Some greens related to broccoli provide glucosinolates. This green group includes bok choy, Chinese cabbage, and horseradish. Isothiocyanates are chemicals released from the glucosinolates when you chew or crush the plant. When the cells are crushed they release an enzyme called myrosinase which liberates the istohiocyanates. The liver induces enzymes to detoxify the isothiocyanate and in the process upregulates a family of enzymes in your liver that protect your from other toxins.