Effects of conventional cooking techniques on the in vitro antioxidant property and total phenolic content of wooly joint prickly pear (Nopalea cochenillifera (Linn.) Salm-Dyck)

• Main Authors: Salarda, Neil Aldrich Mamitag, Aldas, Alyson Kathleen Nazarrea
• Format: text
• Language: English
• Published: Animo Repository 2023
• Subjects: Nopalea cochinellifera; Phenols; Biochemistry
• Online Access: https://animorepository.dlsu.edu.ph/etdb_chem/4; https://animorepository.dlsu.edu.ph/cgi/viewcontent.cgi?article=1006&context=etdb_chem
• Institution: De La Salle University

There have been efforts in investigating natural products for their antioxidant properties and the compounds responsible for such biological activity in order to combat diseases as a result of oxidative stress. As such, the present study determined the antioxidant activity, total phenolic content and bioactive compounds of Nopalea cochenillifera (Linn.) Salm-Dyck cladodes and fruits using DPPH assay, Folin-Ciocalteu assay and GC-MS, respectively. Considering that the cladodes can either be eaten raw or cooked, the present study also determined the effect of conventional cooking techniques on the antioxidant and total phenolic content of cladodes. Results showed that both the methanol and dichloromethane extracts of the raw cladodes and fruits exhibited DPPH scavenging activity in a dose-dependent manner. The cladodes exhibited lower IC50 values than the fruits in both methanol and dichloromethane extracts, indicating that cladodes had higher DPPH scavenging activity than fruits. This difference could be attributed to the difference in the amount and presence of bioactive compounds between the cladodes and fruits. Blanching, boiling, steaming and microwaving decreased the DPPH scavenging activity of cladodes, which could be due to the loss of bioactive compounds by leaching, thermal degradation and oxidation. In addition, the cutting of cladodes could have also contributed to the decrease in its antioxidant activity. Lastly, it was observed that methanol extracts obtained a higher DPPH scavenging activity than dichloromethane extracts. Folin-Ciocalteu assay revealed that the methanol and dichloromethane extracts of the raw cladodes and fruits contained phenolic compounds, with the fruit having more phenolic compounds than the cladodes. Methanol also extracted more phenolic compounds compared to dichloromethane. The cooking techniques decreased the total phenolic content of the dichloromethane extract of the raw cladodes, while no significant difference in total phenolic content between the raw and processed cladodes was found in the methanol extract, except for the boiling method. GC-MS analysis putatively determined five (5) bioactive compounds present in the methanol and dichloromethane extracts of the raw cladodes and fruits, with all of them having antioxidant activity. Results clearly showed that N. cochenillifera cladodes and fruits could be exploited for their antioxidant activity and bioactive compounds, and could be used as support in using N. cochenillifera as a medicinal food. However, further experiments must be employed to strengthen the results, such as performing other in vitro antioxidant assays and in vivo antioxidant experiments. At the same time, methanol was found to be a more efficient solvent in terms of extracting phenolic compounds and possibly other antioxidant compounds. Furthermore, the results showed that the conventional cooking techniques affected the DPPH scavenging activity and total phenolic content of cladodes. Further experiments could be conducted to determine the best cooking parameters to minimize the effect on the antioxidant activity and bioactive compounds of cladodes. Lastly, other bioactive components could be explored by using other characterizing techniques such as HPLC, LC-MS and NMR. Keywords: Nopalea cochenillifera, cooking techniques, antioxidant activity, DPPH assay, total phenolic content, Folin-Ciocalteu assay, gas chromatography-mass spectrometry