after NMR analysis how can a researcher know that the compound is known or unknown. Whether H1 NMR is sufficient or C13 NMR has also to be performed. What other requirements are?
You may need to do additional work to confirm the structure such as x-ray crystallography, circular dichromism, UV-profile etc. After you have characterised a compound it is important to consult the literature to see if this compound has been previously reported. Search the compound using its IUPAC name. Also search for the compound by the natural product source you extracted it from or the genus. The best way however is to used chemical databases such as CHEMnetBASE