Yes, i would recommend that you take biological replicates.

Each one ( fresh, oven or air dried) is a treatment on its own. You will analyse them independently and compare their polyphenol contents. Sometimes the difference between treatments may not be considerable: the only way to tell for sure that the difference you are noting is true and not an artifact is to record replicate readings for each sample type, find the average, and the SD/SEM.

Replicates help to show variation in the experiment so that statistical tests can be applied to evaluate any differences in the means.

Triplicate measurements are the standard, but at the very least, take duplicate readings. Find the standard in your area of research and comply, otherwise journals may refuse to publish

I fully agree with the above answer. Analysing replicates is essential in obtaining meaningfull and, even more trustworthy, results. Differences between apparently identical samples may be quite large, making the analyses of replicates essential.I

Thank you for your insights 💖

Sometimes, a specific plant, the different plant bases, some its organs and even a primary and secondary metabolites could be considered as a sample size in which including different observations according to the purpose of the study. However, this happens when comparative assessments are needed. This is entirely related to the objectives of the research. It should be noted that doing such a studies makes cause to raise up the research costs.

Maintaining biological replicates will definitely reduce the sampling error and influence of environmental and edaphic factors and even sample collection will have seasonal variations and once confirmed a lot these screening and can fix the season'location and number of replicates.