SAN FRANCISCO (MarketWatch) -- Shares of Amazon.com Inc. were active Friday evening as investors continued to digest the company's quarterly results, while shares of Herbalife Ltd. shot up 18% after the nutritional supplement maker said that it has received a buyout offer.

Shares of Herbalife jumped 18% to $39.16. The company said it has received an acquisition offer of $38 a share from Whitney V L.P. and its affiliates. The offer represents a 14.8% premium to the Herbalife's regular-session closing price of $33.10.

Whitney and its related parties already own roughly 27% of Herbalife's outstanding stock. Herbalife said it would review the offer but gave no assurances that it would accept it.