Hi Ram,
Thank you very much for using Syncfusion Products.
As you mentioned, we have created a sample in which the text "bold" in "some text in bold" is formatted as bold using Rich Text functionality of XlsIO. We have attached the sample below. Please find the sample and let us know if this helps you.
Sample Link:
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=RichTextFormattingSample-57057419.zipPlease let us know if you need any further assistance.
Thanks,
Pauline Bosco.