## 3 Results
Earlier authors have reported the relationships between phenolic content and antioxidant activity; while some authors found a high correlation between the phenolic content and the antioxidant activity [26; 27; 28; 29; 30], others found no relationship [31; 32]. In our study we found a strong relationship between the phenolic contents and antioxidant activity. These results signify that in terms of enhanced bioactivity of the Graviola leaf extraction, the most ideal extraction method was the SMW-WE method, which uses sonowaves combined with the microwave technology. This dual extraction method lasted only 7 min, hence less time consuming compared to the conventional extraction methods which required PB-WE = 30 min and CB-WE, about 20 min. The standalone microwave based extraction (MW-WE) was also significantly less time consuming (2 min) and more efficient, while the sonication method (S-WE) required 15 min and was less efficient. Thus as shown by these results, the neoteric sono-microwave conjunct methodology was optimized as the most ideal and successful protocol for enhanced extraction of bioactive components from Graviola leaves. UV-Visible spectrometric analysis (Figure 3) of the extracts obtained using the five different methodologies indicated the presence of extensive peaks in the SMW-WE, CB-WE, MW-WE extracts compared to the PB-WE and S-WE methods. As revealed from the earlier results pertaining to the total phenolics, flavonoids and antioxidant activity, where SMW-WE, CB-WE, MW-WE recorded higher values, these UV results also confirm that enhanced extraction was enabled by these methodologies  
Figure 2: Comparative antioxidant properties of the Graviola leaf extracts using **(A)** DPPH assay and **(B)** FRAP assay. compared to PB-WE and S-WE methods. The fruits, leaves, stems and roots of Graviola are known to be rich in flavonoids, isoquinoline alkaloids and annonaceous acetogenins [2; 33; 34; 35; 36; 37; 38; 39; 40]. It is reported [41; 42] that absorption peaks from 200 to 230 nm are characteristic of acetogenins. In case of PB-WE and S-WE extracts we find that specifically a broad band peak in this wavelength dominating. While the other extracts too show peaks within this range, other peaks possibly belonging to other flavonoids, alkaloids are also observed. Pityochemical screening conducted on leaves extracts of _A. muricata_ revealed the presence of following classes of compounds: alkaloids, flavonoids, terpenoids, coumarins and lactones, anthraquinones, tannins, cardiac glycosides, phenols, phytosterols, and saponins [43]. These are reported from both the ethanolic and water extracts of Graviola leaves. Generally, it is known that the presence of alkaloids, flavonoids, terpenoids, coumarins and lactones, anthraquinones, tannins, cardiacglycos, phenols, phytosterols, and saponins validate the economic importance of _A. muricata_ leaves extracts for extensive use in medicine both traditionally and pharmaceually [33]. These compounds were reported for their antimicrobial, antifouling, antioxidant, hypo-cholesterol, anti-tuberculosis, insecticidal, anti-inflammatory, nematicidal, pesticidal, anti-androgenic, hemolytic 5-alpha reductase inhibitory, anticancer, anti-diuretic, immune-stimulatory, anti-diabetic. antihistaminic, insectifugal, anti-eczemic and anti-acne properties [33].