Shares of Groupon (GRPN) touched a new all-time low of $4.34 Tuesday following a downgrade by Barclays (BCS), but rebounded slightly in choppy trade at the session's close. 

Groupon's shares are down about 40% since the company posted disappointing quarterly results a week ago. They opened lower on Tuesday then rebounded as much as 2% higher earlier in the afternoon before retreating again later the day, closing down 2.4% to $4.54.

Barclays slashed its price target on the daily deals site to $4 from $15 and cut its rating to “underweight” from “overweight,” citing a slowdown in Groupon's core business.

"There was an unexpected change in Groupon’s business model whereby product sales, which have roughly one-third the gross margin contribution of core service/local deals, represented the majority of growth," Barclays analyst Mark May said in a report. 

While Groupon's lower-margin discount business has been booming, it could weigh on the company’s profit margins, May said. Groupon typically buys products sold in its “Goods” business in bulk at a discount then sells them to customers at a higher price.

Compounding the pressure on margins is a decline in customer growth, which May said could force Groupon to rely more heavily on advertising and lift marketing costs.

While the daily deals site, which offers discounts on a variety of activities from manicures to four-course dinners, posted earnings that topped Wall Street expectations last week, sales of $568 million fell widely short of the consensus.

Follow Jennifer Booton on Twitter at @Jbooton