Gas chromatography-mass spectrometry (GC-MS) analysis identified 53 phytochemicals in the combined product, with 18 known for their biological activities. Notable compounds included farnesol, cystamine, cystine, metaraminol, dl-phenylephrine, and two substituted amphetamine compounds. Three phytochemicals exhibited anticancer properties: farnesol , and an imidazole derivative resembling the drug Ribavir . These compounds could serve as valuable starting materials, intermediates, or derivatives in pharmaceutical production. For aspirin, the peaks at 3488.8 cm -1 (O-H stretching), 2870.1 cm -1 , 2959.5 cm -1 , and 2698.6 cm -1 (C-H stretching, alkanes), 2586.8 cm -1 (S-H stretching), 1837.6 cm -1 and 1804.0 cm -1 (C=O stretching, anhydrides), 1751.8 cm -1 (C=O stretching, esters), 1684.8 cm -1 (C=C stretching, alkenes), 1483.5 cm -1 and 1416.6 cm -1 (C-H bending, alkanes) disappeared. For guava extract, the peaks at 3693.8 cm -1 (O-H stretching), 2851.4 cm -1 (C-H stretching, alkanes), and 1994.1 cm -1 (C≡C stretching, alkynes) also disappeared. In the combined product, new peaks emerged at 3235.3 cm -1 (O-H stretching from guava extract), 2918.5 cm -1 (C-H stretching, alkanes from guava extract), 2105.9 cm -1 (C≡C stretching, alkynes from aspirin solution), 1455.7 cm-1 (C-H bending, alkanes from guava extract), along with peaks at 1748.1 cm -1 (C=O stretching, esters from aspirin solution), 1677.3 cm -1 (C=C stretching, alkenes from aspirin solution), 1602.8 cm-1 (C=C stretching, aromatics from aspirin solution), and 1453.7 cm -1 (C-H bending, alkanes from aspirin solution). These changes in peak positions and transmittance levels suggest significant structural modifications, with reduced transmittance indicating a higher concentration of compounds with specific functional groups. The combined presence of peaks from both guava extract and aspirin solution confirms the formation of a new compound with modified structural characteristics, suggesting that the combination of aspirin with guava extract leads to a novel product with potentially enhanced antibacterial properties. This method can be further explored by reacting non-bioactive constituents of one plant extract with those of another, bioactive constituents of one plant with non-bioactive constituents of another, or using different solvents and isolated compounds. Various combinatorial reactions can be designed to achieve the desired results.