The loquat cultivar Golden Nugget (leaves, flowers and fruits), which has potential commercial importance in Chile, was analyzed for targeted bioactive composition (total phenolic contents: TPC, phenolic profiles and triterpenic acids) and in vitro bioactivity such as antioxidant capacity (AC) and inhibitory activity against enzymes relevant for hyperglycemia (α-amylase and α-glucosidase) and hypertension (angiotensin I-converting enzyme, ACE-I) management. Leaves and flowers had higher TPC and AC than fruits and hydroxycinnamic acid derivatives were found in all structures by HPLC. Chlorogenic acid and quercetin derivatives were detected only in leaves and flowers, which also inhibited the α-amylase and α-glucosidase enzymes, but flowers showed the highest anti-hyperglycemia activity. No inhibition of ACE-I and hyperglycemia-relevant enzymes were found in loquat fruits; additionally, TPC and AC were high at the green stage. Loquat leaves and flowers are sources of phenolic bioactives with potential for diet-based hyperglycemia management. No triterpenic acids were found in any of the loquat parts.