U.S. stocks sank lower in afternoon trading Tuesday as shares of Apple Inc. (NASDAQ:AAPL), the world’s most valuable company, dropped to a six-month low. Five out of the 10 Standard and Poor's 500 sectors traded lower, led by a more than 1 percent decline in utilities, while materials was the biggest gainer, up nearly 1 percent.

The Dow Jones Industrial Average (INDEXDJX:.DJI) declined 24.45 points, or 0.14 percent, to 17,573.75. The S&P 500 index (INDEXSP:.INX) lost 1.52 points, or 0.07 percent, to 2,096.54. And the Nasdaq composite (INDEXNASDAQ:.IXIC) fell 7.33 points, or 0.14 percent, to 5,108.47.

Shares of Dow component Apple sank 3 percent Tuesday, extending losses after the tech giant technology giant fell below its 200-day moving average a day earlier for the first time since September 2013.

The iPhone maker hit a record high of $133 on Feb. 23, and hit a market value of nearly $775 billion. On Feb. 10, Apple became the first company ever to hit a market capitalization of more than $700 billion.

Since then, the stock has lost nearly 9 percent of its value, with a market capitalization of $675 billion -- based on the close of trading Monday -- losing $100 billion in market value since February.

Apple’s market cap lost $60 billion in just seconds July 21 after the company’s iPhone sales disappointed last quarter, erasing a value that is equivalent to the market cap of Priceline Group Inc. ($64 billion), the world's largest online travel services company, and warehouse club operator Costco Wholesale Corp. ($63 billion).

Following the company’s earnings announcement last month, FBR Capital Markets maintained its Outperform rating on Apple, but lowered its 12-month price target from $185 to $175.

Apple's stock fell 3.3 percent Tuesday to as low as $113.25 in afternoon trading. Shares of Apple have still gained 24 percent in the last 12 months.

Meanwhile, Microsoft Corporation (NASDAQ:MSFT) was the biggest gainer in the Dow, adding more than 1 percent. The gains come after the world’s largest software company got its Windows 10 launch off to a strong start, with its usage share jumping by four times in just three days, Computerworld.com reported, citing Irish metrics company StatCounter.

The increase was much larger than Microsoft’s last free upgrade of Windows 8.1 in October 2013.

Shares of Microsoft have gained nearly 8 percent in the last 12 months.

Meanwhile, Greek stocks dropped more than 4 percent at the open Tuesday in its second day of trading following a five-week shutdown. The exchange pared losses to close the session 1 percent lower after the ASE Stock Index plunged 16.2 percent a day earlier, its worst drop on record.

The Greek financial markets and banks remain in “zombie mode,” said Ilya Feygin, managing director at WallachBeth Capital, as Greek traders on the stock exchange are restricted from trading normally. “The financial system in Greece is not a real financial system right now, which is bad for the Greek economy.”

Oil prices recovered slightly Tuesday after plunging 5 percent a day earlier, hitting a six-month low on concerns over China's economic growth weighed on investors’ outlook.

West Texas Intermediate (WTI) crude, the benchmark for U.S. oil prices, added nearly 2 percent to $45.99 per gallon barrel for September delivery on the New York Mercantile Exchange. On the London ICE Futures Exchange, Brent crude, the global benchmark for oil prices, rose 1 percent to $50.04.