A non-conventional approach for obtaining phenolic antioxidants from red guava (Psidium guajava L.) by-products

The recovery of phenolic antioxidants from agro-industrial by-products using non-conventional techniques is a powerful tool to explore the bioactive potential of natural sources. Therefore, it is imperative to analyze the most suitable method to investigate a plant material's phenolic composition. This study used ultra-turrax (UTE), ultrasonic bath (BUAE), and pressurized liquid (PLE) for soluble phenolic extraction from guava's pulp and processing waste. UTE at 25 degrees C for 1 h yielded the highest concentration of total phenolics and flavonoids from guava pulp, while PLE for 30 min at 60 degrees C/10 MPa presented the best performance for flavonoids and condensed tannins recovery from guava waste. PLE produced extracts with 39 phenolics and high antioxidant capacity. Besides, scopoletin, resveratrol, and naringin are being reported for the first time in this fruit. These results suggest possible alternatives for the recovery of bioactive compounds, which may be used to develop nutraceuticals and/or functional foods. Practical applications Upon guava processing, 30% of fruit's total volume is lost in the form of by-products (seeds, peels, and pulp leftovers). Evidence points out that this fraction, along with guava's pulp, is rich in phenolics with antioxidant properties. An extraction procedure should be conducted to recover these compounds. However, conventional techniques are laborious, time-consuming, and they generally use a large amount of toxic organic solvent. Ultra-turrax-UTE, ultrasonic bath-BUAE, and pressurized liquid-PLE are non-conventional approaches that make possible the reduction of solvents and the recovery of selected phenolics not possible with conventional techniques. These extracts could be further applied to lipid-rich foods as a natural antioxidant system and/or as an ingredient in the development of nutraceuticals and functional foods.

Automated summary

The recovery of phenolic antioxidants from agro-industrial by-products using non-conventional techniques is an effective approach to explore the bioactive potential of natural sources. This study found that ultra-turrax, ultrasonic bath, and pressurized liquid extraction are the most suitable methods for phenolic extraction from guava's pulp and processing waste. The extracts obtained have high antioxidant capacity and several compounds were discovered for the first time in the fruit.