What's the fastest way to lose a deal on Shark Tank? Slight one of the show's leading investors. 

Dr. Sarath Malepati was presenting his line of immune support pills called EZC Pak on Sunday's episode when Lori Greiner accused him of ignoring her and focusing on her male counterparts. 

"I'm talking to you and you're looking over at Mark [Cuban]," Greiner told Malepati, after trying to engage in a conversation about his product. "I feel like you don't respect me as a female sitting here." 

The drama unfolded after Malepati pitched EZC Pak, which sells a five-day treatment pack of supplements for $19.99 at chain retailers. He told the Sharks on ABC's business reality program that he was seeking $125,000 for 5 percent equity in his Los Angeles-based business.

"Over the past 10 years, I have been dealing with a lot of complex infections," says Malepati, who worked as a general surgeon before pausing his practice to focus on the business. "In the beginning, we used to be able to treat with antibiotics. Now they don't work anymore." 

Malepati explained that certain bacteria and superbugs are becoming immune to antibiotics, and that's a direct result of consumer-driven health care--specifically, the trend of patients asking doctors for specific treatments. He added that often patients don't need antibiotics to fight viruses. Instead, he said, they need better immune systems, which is how his supplements--which include zinc, echinacea, and vitamin C--could help. 

Cuban responded by challenging Malepati's comments about a health crisis; he argued that patients are getting more information about themselves and their conditions, which serves an important purpose. 

Coming to Malepati's defense, Greiner shared her concern about the overuse of antibiotics and noted that she often turns to zinc when she starts feeling sick. Malepati appeared to barely acknowledge her comments and kept his gaze on Cuban. 

"I'm the one talking to you about antibiotic resistance and how important it is," Greiner told Malepati. "But the fact that when I'm talking to you, you don't even look at me, I'm out." 

Greiner went on to say that perhaps Malepati was still shaken by Cuban's remarks, but that she sensed chauvinism from him. The remaining Sharks, all of whom were male, tried to refocus the conversation on Malepati's numbers--he booked $1.2 million in sales in the past 12 months, he said on the show. However, Cuban, Robert Herjavec, and guest Shark Daniel Lubetzky eventually declined to offer him a deal. 

Kevin O'Leary was the last one left, and after some negotiating with Malepati, the pair settled on a $125,000 investment for a 5 percent stake and a $1 royalty until O'Leary recoups $450,000. 

Not long after the episode aired, O'Leary tweeted in defense of Malepati and included a brief statement from the entrepreneur. "As a person of color and someone who's gone through life with a foreign-sounding name, I know what it feels like to be slighted and overlooked," the statement read. "It was never my intention to avoid eye contact with any of the Sharks, but I understand that's how it was perceived and I apologize." 

Greiner, who's been an investor on the show since its early days, is a powerful ally for entrepreneurs--she often brings her Shark Tank investments on QVC. Eric Child, the founder of adhesives company FiberFix, told Inc. last year that she brings context and compassion to her investments

"As a woman in business, I think it's important for women to speak up for themselves and stand up for themselves in a respectful way," Greiner said on the show. "I don't think I've ever reacted like this on Shark Tank.