The cosmetics industry is in the midst of a significant shift, driven by consumer demand for both natural and sustainable ingredients. This transformation is accelerated by concerns on conventional components like UV filters, known for potential environmental degradation and endocrine disruption. Despite the urgency, natural UV-absorbing alternatives based on chemical light absorption remain scarce. Secondary plant substances (SPS), particularly water-soluble tannins, present a promising possibility. This study investigated the reducing capacities, antioxidant activity, tannin contents, and UV-absorption properties of various plant-based extracts mainly obtained from by-products and residues from the agricultural and food industry. By utilizing side-streams, emerging ingredients are potential factors to contribute to the sustainability of cosmetics. The results revealed that bark and tea grounds exhibited the highest reducing capacities and antioxidant activities, making them potential natural sources. Fruit peels, however, showed relatively low antioxidant capacities. Tannin contents varied significantly among the samples, with wine pomace and bark having the highest levels. The UV-absorption measurements indicated that the extracts had the ability to block UV-A and even some visible light, except for fruit peels and nut shell extracts, which were less suitable for UV protection. These findings provide valuable insights into the properties and potential applications of these natural extracts.