Which HTML tag will be the best for the red part in HTML case?
AFAIK the summary tag has another concept - it consists from the short text and details which could be hidden (collapsed). In the case of the article, basically it is nothing required to hide./
Basic HTML and ARIA do not express much of the semantics of scholarly publications.
But the W3C recommendation "Digital Publishing WAI-ARIA Module 1.0" includes a "doc-abstract" ARIA role that represents abstracts like the one in your example. There is also a proposal for using this and other standards in scholarly publications. Starting with conventional HTML as proposed by Ilan Edri and adding such specialized markup can improve discovery and interpretation of your content by users of current and future technologies.