As with other citrus fruits, orange pulp is an excellent source of vitamin C (providing 64% of the Daily Value in a 100 g serving).

Vitamin C is involved in the physiology of the nervous system. This antioxidant interacts with self-recycling mechanisms, including its participation in the endogenous antioxidant system.

Oranges contain diverse phytochemicals, including carotenoids (beta-carotene etc.)
The human body converts beta carotene into vitamin A (retinol). Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea. Vitamin A also supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs. 

(Excess vitamin A is toxic, toxic vitamin A levels can occur if you consume too many supplements.)

Sources of Information: medicalnewstoday.com, ncbi.nlm.nih.gov, ods.od.nih.gov & Wikipedia