Phenolics have been positively associated with many health benefits due to their prominent antioxidant activities. Sample extractions are required prior to chromatographic measurements for the determination of phenolics in matrices. Hence, the aim of this study was to assess the stability of 40 phenolic compounds of different families (benzoic acids, benzoic aldehydes, cinnamic acids, catechins, stilbens and flavonols) under conditions of ultrasound-assisted extraction (UAE). The influence on the stability affected by the working temperature between 10 and 70°C applying ultrasounds for 20 minutes was evaluated. As for precisely pinpointing the trigger for the degradation, the extractions were repeated in light protected experiments and by stirring to check their influences on the stability of phenolics apart from the effects of ultrasounds. Regardless the present of light, all studied phenolics were stable up to 50°C with the exception for kaempferol and some light sensitive compounds such as resveratrol, sinapic acid and p-coumaric acid. By light protected UAE, starting at 60°C there were significant degradations of gallic acid (12%) and rutin (16%) whilst other compounds showed degradation starting at 70 o C i.e. p-coumaric (11%), o-coumaric (12%) and resveratrol (21%).