## 3 Results  
The total phenolics, flavonoids and antioxidant activity of the Graviola extracts prepared using the five different methodologies was determined. These parameters are reported to signify the bioactivity of the tested sample. Of the five different methodologies used, the first two, PB-WE and CB-WE were the commonly practiced extraction methods, while the sonication based (S-WE), microwave based (MW-WE) and the dual SMW-WE methods were those that were applied and experimented on for the first time in this report. The successful extraction of the bioactive compounds following the application of the various extraction methods validates the efficiency of the applied extraction protocol. Figure 1A presents the comparative results of the five different protocols on the extraction of bioactive total phenolic substances from Graviola leaves. As observed from the figure, significantly higher phenolic compounds were observed in SMW-WE, MW-WE and CB-WE while PB-WE and S-WE were almost similar. Phenolics are major bioactive compounds known for their health benefits reported to exhibit multiple biological effects, including antioxidant activity. Their scavenging activity is mainly due to their redox properties, which allows them to act as reducing agents, hydrogen donors and singlet oxygen quenchers [21]. The efficient extraction of higher phenolics signifies the efficacy of the extraction technique in leading to enhanced harnessing of the bioactivity of the Graviola leaves. The SMW-WE method is considered superior to the others in this aspect. Flavonoids belong to a large group of polyphenolic compounds having a benzo-\(\gamma\)-pyrone structure and are ubiquitously present in plants. It is reported that secondary metabolites of phenolic nature including flavonoids are indulging in a variety of pharmacological activities [22; 23; 24]. Phenolic acids are secondary metabolites widely distributed in the plant kingdom and are second only to flavonoids in terms of their dominance. So saying, flavonoids play an equilateral role in the bioactivity and are reported to occur in abundance in case of Graviola extracts and participate in the so called'sour sop properties' [25]. The efficient extraction of these vital bioactive components from the Graviola leaves was evaluated in order to rate the efficiency of the five different extraction methods employed. In case of flavonoids (Figure 1B), an almost similar trend with marginal variation was observed. SMW-WE lead to the highest extraction of flavonoids from the Graviola leaves, followed by MW-WE > CB-WE. S-WE was more effective compared to PB-WE in terms of extraction of flavonoids. A recent study demonstrated the importance of flavonoid content in Graviola, where the synergistic interactions among flavonoids and acetogenins in Graviola (_Annona muricata_) leaves conferred protection against prostate cancer [25]. Hence, in this aspect the fact that the SMW-WE method led to enhanced extraction of flavonoids stands highly significant in terms of enhancing it anticancer properties. The antioxidant activities of extracts obtained from employing the five different extraction methodologies were also evaluated using the DPPH and FRAP assays. Figure 2A,B give results of these  
Figure 1: **(A)** Graph showing total phenolics extracted using the five extraction methods; **(B)** Graph showing flavonoid contents from Graviola leaf following extraction using the five different methods. preboiled water extraction (PB-WE); co-boiled water extraction (CB-WE); sonicated water extracts (S-WE); microwave water extracts (MW-WE); sono-microwave water extraction (SMW-WE). assays. DPPH and FRAP assays showed a similar trend where SMW-WE extraction method yielded extracts exhibiting the highest antioxidant activity, followed by PB-WE extracts. It was interesting to observe that the antioxidant activity of the extracts, varied from the total phenolics and flavonoids where PB-WE recorded the least. S-WE and MW-WE showed high antioxidant activity too. The least antioxidant activity was observed in CB-WE.